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THE  NEWER  KNOWLEDGE  OF  NUTRITION 


•The 


THE  MACMILLAN  COMPANY 

NEW   YORK   •    BOSTON   •    CHICAGO    •   DALLAS 
ATLANTA    •    SAN   FRANCISCO 

ly^ACMILLAN  &  CO.,  Limited 

LONDON    •   BOMBAY    •  CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA.  Ltd. 

TORONTO 


THE  NEWER  KNOWLEDGE 
OF  NUTRITION 

THE  USE  OF  FOOD  FOR  THE  PRESERVATION 
OF  VITALITY  AND  HEALTH 


BY 
E.  V.  McCOLLUM 

SCHOOL   OF   HYGIENE   AND    PUBLIC   HEALTH,    TECE 
JOHNS   HOPKINS    UNIVERSITY 


ILLUSTRATED 


THE  MACMILLAN  COMPANY 
1918 


All  rights  reserved 


Copyright,  1918 

By  the  MACMILLAN  COMPANY 

Set  up  and  electrotyped.  Published  October,  1918. 


Qt\m 

'/f/r 


PREFACE 

The  need  for  knowledge  of  nutrition  was  never 
greater  than  at  the  present  time  when  so  large  a 
part  of  the  energies  of  the  people  of  Europe  and 
America  are  absorbed  in  the  activities  of  war.  The 
demoralization  of  agriculture  over  wide  areas,  to- 
gether with  the  shortage  of  tonnage  for  the  trans- 
portation of  food,  have  reduced  the  food  supply  of 
a  number  of  nations  to  the  danger  point,  and  have 
cut  off  in  great  measure  the  opportunity  for  securing 
the  variety  which  exists  in  normal  times. 

The  investigations  of  the  last  few  years  have, 
fortunately,  led  to  great  advancement  in  our  knowl- 
edge of  what  constitutes  an  adequate  diet.  Such 
knowledge  can,  if  rightly  applied,  greatly  assist  in 
enabling  us  to  make  use  of  our  food  supply  in  a 
manner  which  will  avoid  mistakes  sufficiently  serious 
to  become  reflected  in  a  lowering  of  our  standard 
of  pubhc  health.  It  seems  certain  that  pellagra  is 
the  sequel  to  the  adherence  to  a  faulty  diet  for  such 
a  period  as  to  materially  reduce  the  powers  of  re- 
sistance of  the  body  to  infection,  and  reasons  are 
presented  in  support  of  the  view  that  there  is  a 


vi  PREFACE 

much  closer  relationship  between  the  character  of 
the  diet  and  the  incidence  of  tuberculosis  than  has 
hitherto  been  believed.  This  view  is  offered  in  the 
present  discussion  as  an  invitation  to  criticism,  in 
the  hope  that  new  data  either  in  support  or  refuta- 
tion of  its  validity  will  be  presented.  If  it  shall  be 
definitely  proven  that  faulty  diet  is  the  chief  factor 
in  the  etiology  of  this  disease,  and  that  pellagra, 
is,  as  the  Thompson-McFadden  Commission,  Jobling 
and  Peterson  and  others  believe,  caused  by  infection, 
it  will  establish  that,  as  the  author  suggests,  large 
groups  of  people  are  at  the  present  time  making 
serious  errors  in  the  selection  of  foods.  Regardless 
of  the  outcome  of  future  studies  relating  to  the  im- 
portance of  diet  to  the  etiology  of  these  diseases,  a 
non-technical  presentation  of  the  kinds  of  combina- 
tions of  our  natural  foods  which  induce  good  or 
faulty  nutrition  in  animals,  should  be  of  service  in 
showing  the  inadequacy  of  the  practice,  which  is 
still  in  vogue,  of  regarding  calories  as  the  factor  of 
prime  importance  in  the  planning  of  the  diet. 

From  the  data  discussed  in  the  following  pages  it 
will  be  evident  that  the  idea  that  freedom  of  choice, 
and  variety  of  food  sources  for  the  diet  will  prevent 
any  faults  in  the  diet  from  becoixdng  serious,  is  no 
longer  tenable,  especially  if  one  is  willing  to  admit 


PREFACE  vii 

the  existence  of  many  degrees  of  gradation  of  mal- 
nutrition, not  recognizable  except  in  their  effects  on 
the  individual  over  a  long  period  of  time.  The 
author  recently  enjoyed  with  a  friend,  a  dinner 
which  consisted  of  steak,  bread  made  without  milk, 
butter,  potatoes,  peas,  gravy,  a  flavored  gelatin 
dessert  and  coffee.  The  meal  was  appetizing  and 
satisfying,  but  such  a  diet  of  seeds,  tubers  and  meat 
would  not  promote  health  in  an  experimental  animal 
over  a  very  long  period. 

The  Hterature  which  has  a  bearing  on  the  applica- 
tion of  modern  research  to  the  practical  problems 
of  human  nutrition  has  become  somewhat  extensive 
and  is  scattered  in  technical  journals,  and  is  not 
readily  accessible,  or  easy  to  read  in  proper  sequence. 
During  the  present  year  the  author  had  the  pleasure 
of  presenting  an  interpretation  of  this  literature  in 
the  Thomas  Clarence  Cutter  Lectures  at  the  Harvard 
Medical  School.  Believing  that  the  pubhcation  of 
these  lectures  would  serve  to  answer  many  of  the 
questions  which  have  been  asked  in  numerous  letters 
from  the  public,  they  have  been  edited  and  presented 
in  their  present  form. 

It  is  a  pleasure  to  acknowledge  the  author's  in- 
debtedness to  those  who  have  assisted  in  carrjdng 
out  the  experimental  work  which  made  possible  the 


viii  PREFACE 

discussion  of  nutrition  offered  in  this  book.  Nearly 
three  thousand  feeding  experiments  varying  in  length 
from  six  weeks  to  four  years  have  been  observed. 
Special  appreciation  should  be  accorded  to  Miss 
Marguerite  Davis  who  assisted  with  the  early  work, 
in  the  first  two  years  of  which  no  interpretation  of 
the  cause  of  success  or  failure  of  our  experimental 
animals  was  possible,  and  to  Miss  Nina  Simmonds 
and  Miss  Helen  T.  Parsons  for  their  keen  interest 
and  never-failing  loyalty  to  the  work. 

E.   V.   McCOLLUM. 

The  Johns  Hopkins  University 
School  of  Hygiene  and  Public  Health, 
Baltimore,  Md. 


CONTENTS 

CHAPTER  PAGE 

I.  The  Biological  Method  for  the  Analysis  of  a 

Food-stuff 1 

II.  Experimental  Scur\t  and  the  Dietary  Properties 

OF  Vegetables 34 

III.  The  Vegetarian  Diet 53 

IV.  The  Foods  of  Animal  Origin 69 

V.  The  Diseases  Referable  to  Faulty  Diet,  or  the 

So-called  '"Deficiency  Diseases" S3 

\l.  The  Nursing  Mother  as  a  Factor  of  Safety  in  the 

Nutrition  of  the  Suckling 116 

VII.  Practical  Considerations  wbich  Should  Guide  in 

THE  Planning  of  the  Diet 130 

Introduction  to  the  Legends  to  the  Charts  .  .  .   154 

Bibliography 191 

Index 197 


IX 


THE  NEWER  KNOWLEDGE  OF  NUTRITION 


THE  NEWER 
KNOWLEDGE  OF  NUTRITION 

CIL\PTER  I 

THE    BIOLOGICAL    METHOD    FOR    THE    ANALYSIS    OF    A 

FOOD-STUFF 

Our  knowledge  of  nutrition  has  progressed  hand 
in  hand  with  the  development  of  the  science  of 
Chemistry.  Chemical  science  gave  us  the  clue  to  an 
understanding  of  the  nature  of  the  food-stuffs  and 
the  changes  which  take  place  in  digestion,  as  well 
as  an  appreciation  of  some  of  the  secrets  of  the 
metabohc  processes  which  take  place  within  the 
tissues  of  the  body.  Chemistry  will  continue,  as 
time  goes  on,  to  aid  in  extending  our  knowledge  of 
the  finer  processes  of  physiology.  Nevertheless, 
it  has  been  possible  for  a  time  to  advance  very  rapidly 
in  the  study  of  nutrition,  from  the  technical  as  well 
as  from  the  practical  standpoint,  by  a  systematic 
feeding  of  simplified  diets  to  animals.  The  results 
were  interpreted  on  the  observations  as  to  the  abihty, 
or  failure,  of  the  animals  to  develop  normally,  as 
the  diets  were  modified.  Progress  has  resulted  in 
the  past,  and  will  continue  in  the  future  to  come 
from  the  judicious  division  of  labor  between  the 

1 


2       THE  NEWER  KNOWLEDGE  OF  NUTRITION 

study  of  food  problems  by  chemical  methods,  and 
by  animal  experimentation.  In  this  brief  exposition 
of  the  present  situation  respecting  our  knowledge  of 
foods  and  nutrition,  it  is  desirable  that  the  reader 
should  appreciate  the  viewpoint  of  the  investigator, 
and  should  understand  the  hne  of  reasoning  by  which 
the  successive  steps  in  the  progress  of  the  last  few 
years  have  been  attained.  A  brief  historical  account 
of  the  steps  by  which  research  in  this  field  have  been 
developed  will  serve  this  purpose,  and  at  the  same 
time,  will  illustrate  the  mental  processes  of  a  student 
engaged  in  the  task  of  bringing  order  into  a  field  of 
scientific  inquiry  where  before  there  was  no  clear 
understanding. 

A  plant  structure,  or  an  animal  body  is  an  exceed- 
ingly complex  mixture  of  chemical  substances,  many 
of  which  are  themselves  individually  as  complicated 
in  their  structure  as  the  most  complex  machine. 
The  first  step  in  the  direction  of  reaching  an  under- 
standing of  the  chemistry  of  the  living  mass,  must 
involve  the  separation  and  study  of  the  structural 
units  of  which  the  tissues  are  composed.  This  was, 
indeed,  the  field  of  activity  of  many  organic  and 
physiological  chemists  during  the  nineteenth  century. 
The  fats  and  the  simpler  substances  into  which  they 
can  be  converted  as  in  soap  making;  the  starches  and 
the  simpler  sugars,  and  the  manner  in  which  they 
are  related  chemically;  the  proteins,  bodies  having 
the  properties  of  egg  white,  the  casein  of  milk,  hair, 
etc.,  yet  very  closely  related  in  their  chemical  nature, 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF  3 

since  they  can  all  be  resolved  into  the  same  digestion 
products  in  the  animal  body,  or  in  the  chemical 
laboratory,  have  all  been  carefully  studied  and  wdth 
marked  success.  These  and  a  long  Ust  of  a  thousand 
or  more  relatively  simple  chemical  substances  have 
been  discovered,  and  isolated  in  a  state  of  purity  from 
plant  and  animal  tissues.  They  have  been  studied 
to  determine  their  special  properties,  composition 
and  the  tests  by  means  of  which  they  may  be  recog- 
nized and  identified. 

Through  a  century  of  patient  labor  by  many  able 
men,  an  understanding  of  the  number  and  character 
of  simple  structural  units  into  which  the  tissues  of 
ardmal  or  plant  can  be  separated,  became  reahzed. 
Furthermore,  certain  of  these  smiple  bodies  could  be 
recognized  as  intermediate  products  on  their  way 
toward  being  built  up  into  the  most  highly  organized 
units  of  the  hving  tissues;  others  were  shown  to  be 
degradation  products  resulting  from  the  physiological 
activity  of  the  living  tissues  of  the  plant  or  ardmal. 
Through  these  studies  it  became  established  that  the 
body  of  an  animal  or  the  tissues  of  a  plant  consists 
essentially  of:  proteins,  which  are  peculiar  in  that 
they  contain  about  sixteen  per  cent  of  the  element 
nitrogen,  and  are  complex  in  structure;  starch-like 
substances  and  sugars,  into  which  the  starches  can 
be  easily  converted,  and  fats  and  a  number  of  closely 
related,  and,  in  many  respects,  similar  substances 
known  collectively  as  lipoids.  With  these  there  are 
always  associated  in  the  hving  tissues  more  or  less 


4        THE  NEWER  KNOWLEDGE  OF  NUTRITION 

water  and  a  number  of  mineral  salts.  Numerous 
special  varieties  oi  ^ach  of  these  types  of  substances 
became  known,  and  their  less  obvious  characteristics 
were  described.  Certain  substances  were  found  to 
be  special  products,  found  only  at  certain  times  and 
in  certain  special  locahties,  and  these  became  re- 
garded in  their  true  light,  as  of  subordinate  interest. 
Examples  of  such  are  the  alkaloids,  quinine,  strich- 
nine,  etc.,  the  cellulose  which  serves  as  skeletal  tissue 
for  the  plant  but  is  not  necessary  for  the  animal,  and 
in  the  same  category  belong  the  waste  products  of 
the  Ufe  processes  of  the  animal  body,  most  of  which 
are  not  found  in  plant  substances.  Living  tissues, 
although  always  associated  with  numerous  sub- 
stances, the  exact  importance  of  which  could  not 
be  determined,  were  found  to  consist  essentially  of 
the  proteins,  fats,  sugars,  mineral  salts  and  water. 
These  came  to  be  regarded  even  as  early  as  1840,  as 
the  essential  and  never  failing  constituents  of  plant 
tissues  and  were  regarded  as  the  essential  constituents 
of  an  adequate  diet  for  an  animal. 

The  processes  of  the  digestion  of  food  have  excited 
the  wonderment  and  have  occupied  the  patient 
attention  of  some  of  the  most  earnest  students  of 
physiology  and  biochemistry.  The  chemistry  of  the 
fats,  and  the  starches  and  sugars  being  simpler,  or 
rather  less  complex  than  that  of  the  proteins,  came 
to  be  earher  understood  in  their  essential  features. 
It  was  not  until  toward  the  close  of  the  nineteenth 
century  that  the  nature  and  extent  of  protein  diges- 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF  5 

tion  became  clearly  appreciated.  Soon  after  1900 
the  researches  of  Fischer  revealed  the  great  variation 
in  the  composition  of  proteins  from  different  som^es.^ 
This  discovery  introduced  into  nutrition  studies  the 
idea  of  quahty  in  addition  to  quantity  which  had 
heretofore  seemed  satisfactory  to  students  of  nutri- 
tion. Most  proteins  were  found  to  be  resolved  into 
eighteen  simple  digestion  products  called  amino- 
acids,  and  it  was  found  that  the  proportions  in  which 
these  were  present  in  the  protein  molecule  varied 
greatly  in  the  proteins  from  different  sources.  All 
or  nearly  all  of  these  digestion  products  appear  to 
be  indispensable  constituents  of  an  adequate  diet. 
All  natural  foods  contain  several  proteins  as  the 
extensive  and  valuable  studies  of  Osborne  have 
shown, ^  and  although  there  are  individual  proteins 
which  are  entirely  lacking  in  one  or  more  of  the  essen- 
tial digestion  products  of  proteins,  every  natural  food 
appears  to  contain  more  or  less  of  each  of  them. 
The  proteins  of  any  single  food-stuff  may  be  regarded 
as  biologically  complete,  but  their  biological  values 
differ  greatly,  depending  upon  the  yield  of  the 
several  amino-acids  which  can  be  obtained  from 
them. 

Food  Analysis. — Since  proteins,  carbohydrates, 
such  as  starches  and  sugars,  fats  and  mineral  salts 
came  to  be  regarded  as  the  essential  constituents  of 
the  normal  diet,  it  early  became  the  principal  activity 
of  the  investigator  of  nutrition  problems  to  analyze 
foods  of  every  sort  by  chemical  methods  in  order  to 


6        THE  NEWER  KNOWLEDGE  OF  NUTRITION 

determine  their  content  of  what  were  supposed  to 
be  the  only  essential  food  complexes.  Pronounced 
differences  were  observed  in  the  composition  of  the 
many  substances  which  serve  as  food  for  man  and 
animals.  Meats,  milk,  eggs,  and  a  few  seeds  such 
as  the  pea  and  bean  are  very  rich  in  protein,  the 
cereal  grains  contain  less  of  this  food  substance, 
whereas  the  tubers  and  vegetables,  especially  in  the 
fresh  condition,  contain  but  very  little.  Equally 
great  variations  are  observable  in  the  water  content 
of  foods,  and  in  their  yields  of  fats  and  carbohydrates. 
One  of  the  great  epochs  in  the  development  of  the 
science  of  nutrition,  is  that  in  which  Atwater  and 
his  associates  examined  and  tabulated  in  classified 
form  the  chemical  composition  of  an  extensive  list 
of  human  foods. ^  Following  this,  similar  data  were 
accumulated  in  the  Agricultural  Experiment  Sta- 
tions concerning  substances  used  for  anianal  foods. 
Up  to  about  1900  the  idea  that  there  was  any  varia- 
tion in  the  quality  of  the  proteins  from  different 
sources  did  not  become  generally  appreciated. 

In  the  light  of  the  revelations  in  the  field  of  nutri- 
tion during  the  last  few  years,  it  seems  remarkable 
that  close  students  of  animal  nutrition  accepted  for 
so  long,  without  proof,  the  belief  ihat  the  results  of  a 
chemical  analysis  revealed  the  dietary  values  of 
food-stuffs. 

Disease  and  Diet. — Restricted  diets  of  monotonous 
character  have  produced,  for  centuries,  diseases  in 
man  in  several  parts  of  the  world.     The  only  one 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF         7 

of  these  which  was  at  all  general  in  the  Western 
hemisphere  was  scurv^^,  a  disease  which  caused  much 
suffering  among  sailors  in  the  days  of  the  long  saiHng 
voyages.  It  was  well  understood  that  the  disease 
was  the  sequel  to  the  consumption  of  a  faulty  diet, 
composed  usually  of  biscuit  and  salt  meats,  and  that 
prompt  recovery  resulted  from  the  consumption  of 
liberal  amounts  of  fresh  vegetables  and  fruits. 
Decades  passed  without  any  systematic  attempt  to 
determine  the  cause  of  the  pecuhar  value  of  this 
class  of  foods. 

Pellagra  was  a  scourge  among  the  poorest  of  peas- 
ants in  parts  of  Europe  for  centuries,  and  its  etiology 
has  been  referred  b}^  many  to  the  poor  quality  of  the 
shnple  and  monotonous  diet.  This  disease  was  not 
observed  in  Ajnerica  until  after  1900.  Since  then 
it  has  been  steadily  increasing  in  the  Southern  States. 

Beri-beri  is  a  disease  common  among  the  poorest 
classes  of  the  Orient,  who  limit  their  food  supph^ 
principally  to  polished  rice  and  fish.  It  is  remarkable 
that  not  until  the  year  1897  was  the  first  fertile 
suggestion  made  by  Eijkman,^  as  to  the  nature  of 
the  dietary  fault  which  was  responsible  for  the 
development  of  this  disease. 

]\Ian  has  been  sufficient^  industrious  in  most 
parts  of  the  world  to  secure  for  hunself  a  varied 
diet,  derived  from  the  cereal  grains  and  legumes, 
fruits,  roots  and  tubers,  meats  and  certain  leaves, 
which  he  found  edible.  Beginning  with  the  da^\^l 
of  the  era  of  his  most  rapid  advance  toward  achieve- 


8        THE  NEWER  KNOWLEDGE  OF  NUTRITION 

ment,  he  has  in  many  parts  of  the  world  been  the 
possessor  and  protector  of  flocks  and  herds,  which 
provided  him  with  clothing,  and  a  constant  supply 
of  both  meat  and  milk.  The  importance  of  this  last 
item  in  his  food  supply  we  have  just  now  come  to 
really  appreciate.  It  is  in  order  that  it  may  be  fully 
appreciated  how  great  are  the  differences  in  the 
nutritive  value  of  foods  of  such  a  composition  as  to 
appear  alike  from  the  results  of  chemical  analysis 
that  the  present  account  of  the  investigations  of 
recent  years  was  prepared. 

In  the  year  of  1907  the  author  began  the  study  of 
nutrition  problems  at  the  Wisconsin  Experiment 
Station.  An  inspection  of  the  literature  which  re- 
lated to  nutrition  at  that  time  disclosed  the  fact  that 
the  diet  was  supposed  to  consist  essentially  of  pro- 
tein, carbohydrates  and  fats,  and  a  suitable  amount 
of  several  mineral  salts.  There  were  in  the  literature 
two  papers  which  were  highly  suggestive  that  a  new 
era  was  about  to  dawn  in  this  field  of  research. 
Henriques  and  Hansen,^  believing  that  gliadin,  one 
of  the  proteins  of  wheat,  was  free  from  the  amino- 
acid  lysine,  had  made  up  a  diet  of  purified  gliadin, 
carbohydrate,  fats  and  mineral  salts,  and  had  at- 
tempted to  nourish  on  this  food  mixture,  animals 
whose  growth  was  complete.  It  was  reported  that 
rats  had  been  kept  in  a  state  of  nitrogen  equilibrimn, 
and  even  retention  of  nitrogen  (protein)  was  reported 
during  an  experimental  period  covering  nearly  a 
month.     In  most  of  their  trials  th«  animals  failed 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF  9 

steadily  from  the  time  they  were  confined  to  food 
of  this  character. 

Willcock  and  Hopkins  ^  had  conducted  experiments 
with  similar  food  mixtures,  composed  of  carefully 
purified  food-stuffs  in  which  all  the  constituents 
were  kno^^^l.  When  the  protein  of  the  diet  consisted 
solely  of  zein,  from  maize,  the  mice  lived  but  a  few 
days.  T^lien  to  this  food  the  amino-acid  trypto- 
phane, wliich  is  not  obtained  on  the  digestion  of 
zein,  was  added  to  the  diet,  the  animals  hved  dis- 
tinctly longer  than  without  this  addition.  All  ex- 
perimental work  with  such  diets  indicated  that  they 
were  unable  to  support  well-being  in  a  young  animal 
during  growth  over  a  prolonged  period.  It  was  an 
interest  in  these  results,  and  a  desire  to  know  why 
such  food  mixtures,  which  comphed  with  all  the  re- 
quirements of  the  chemist  and  the  dietitian,  failed 
to  properly  nourish  an  animal  that  led  to  the  decision 
that  the  study  of  nutrition  offered  a  promising  field 
of  activity. 

At  the  Wisconsin  Experiment  Station  there  was  in 
progress  at  that  time  an  experiment  which  greatly 
strengthened  the  author's  conviction  that  the  most 
profitable  point  of  attack  for  the  study  of  the  prob- 
lems of  nutrition,  lay  in  the  study  of  greatly  sim- 
plified diets  so  made  up  that  every  component  should 
be  kno^\^l.  It  seemed  that,  emplo^dng  such  diets, 
and  by  the  systematic  addition  of  one  or  more  purified 
substances  known  to  be  found  in  natural  foods,  or  in 
animal  tissues,  it  should  be  possible  to  arrive  at  the 


10      THE  NEW^R  KNOWLEDGE  OF  NUTRITION 

solution  of  the  problem  of  just  what  chemical  com- 
plexes are  necessary  in  the  diet  of  the  liigher  ani- 
mals. 

The  above  experiment  was  based  upon  earlier 
work  by  Professor  S.  M.  Babcock,  and  was  suggested 
by  him,  and  carried  out  at  first  by  Professors  Hart 
and  Humphrey,  and  later  with  the  cooperation  of 
Mr.  Steenbock  and  the  author."^  In  this  experiment 
the  object  w^as  to  determine  whether  rations,  so  made 
up  as  to  be  ahke,  in  so  far  as  could  be  determined  by 
chemical  analysis,  but  derived  each  from  a  single 
plant,  would  prove  to  be  of  the  same  value  for  growth 
and  the  maintenance  of  vigor  in  cattle. 

The  ration  employed  for  one  group  of  animals  was 
derived  solely  from  the  wheat  plant,  and  consisted 
of  wheat,  wheat  gluten  and  wheat  straw;  for  a  second 
group  the  ration  consisted  entirely  of  com  plant 
products,  and  included  the  corn  kernel,  corn  gluten, 
a  by-product  of  the  corn  starch  industr^^,  and  the 
leaves  and  stalks  of  the  corn  plant  (corn  stover); 
the  third  group  derived  their  ration  solely  from  the 
oat  plant,  being  fed  entirely  upon  rolled  oats  and 
oat  straw.  There  was  a  fourth  group  which  it  was 
supposed  would  serve  as  controls,  which  was  fed  a 
ration  having  the  same  chemical  composition,  but 
derived  from  about  equal  parts  of  wheat,  corn  and 
oat  products. 

The  animals  employed  were  young  heifer  calves 
weighing  about  350  pounds,  and  were  as  nearly 
comparable  in  size  and  vigor  as  could  be  secured. 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF        11 

They  were  restricted  absolutely  to  the  experimental 
diets,  and  were  well  cared  for.  They  were  given  all 
the  salt  (XaCl)  they  cared  to  eat,  and  were  allowed 
to  exercise  in  an  open  lot  free  from  vegetation.  Their 
beha\'ior  during  gi'owth,  and  in  performing  the  func- 
tions of  reproduction  were  extremely  interesting. 
All  gi'ouiDS  ate  practically  the  same  amount  of  feed, 
and  digestion  tests  showed  that  there  was  no  dif- 
ference in  the  digestibihty  of  the  three  rations. 

It  was  not  until  the  animals  had  been  confined  to 
their  experimental  rations  for  a  year  or  more  that 
distinct  differentiation  m  then'  ajDpearance  was  easily 
observable.  The  cox^n  fed  gi'oup  were  sleek  and  fine 
and  were  e\'idently  in  an  excellent  state  of  nutrition. 
In  marked  contrast  stood  the  wheat  fed  group. 
These  anmials  were  rough  coated  and  gaunt  in 
appearance  and  small  of  ghth  as  compared  with 
those  fed  the  corn  plant  ration.  The  weights  of 
the  two  groups  did  not  differ  in  a  significant  degi^ee. 
The  groups  fed  the  oat  plant  ration  and  the  mixture 
of  the  three  plants,  leaf  and  seed,  stood  intermediate 
between  the  two  lots  just  described.  The  assumption 
that  the  animals  receiving  the  mixture  of  products 
would  do  better  than  any  of  the  others,  and  thus 
serve  as  the  standard  gi^oup  for  controls  was  not 
realized.  The  corn  fed  animals  were  at  all  times  in 
a  better  state  of  nutrition  than  were  those  receiving 
the  greater  variety  of  food  materials. 

The  reproduction  records  of  these  animals  are  of 
special  interest.     The  com  fed  heifers  invariably 


12     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

carried  their  young  the  full  term,  and  the  young 
showed  remarkable  vigor.  All  were  normal  in  size 
and  were  able  to  stand  and  suck  within  an  hour 
after  birth  as  is  the  rule  with  vigorous  calves.  All 
lived  and  developed  in  a  normal  manner.  The  young 
of  the  wheat  fed  mothers  were  the  reverse  in  all 
respects.  All  were  born  three  to  four  weeks  too 
soon,  and  all  were  small  and  weighed  on  an  average 
forty-six  pounds,  whereas  the  young  of  the  corn  fed 
annuals  weighed  73  to  75  pounds  each.  This  weight 
is  normal  for  new-born  calves.  The  young  were 
either  dead  when  born  or  died  within  a  few  hours. 
The  young  of  the  mothers  which  had  been  grown  on 
the  oat  plant  were  almost  as  large  as  those  from  the 
corn  fed  mothers,  the  average  weight  being  71 
pounds.  All  of  them  produced  their  calves  about 
two  weeks  too  soon.  One  of  the  four  was  born  dead, 
two  were  very  weak  and  died  within  a  day  or  two 
after  birth,  the  fourth  was  weak,  but  with  care  it 
was  kept  alive.  The  young  of  the  cows  fed  the 
mixture  of  the  three  plants  were  weak  in  most  cases, 
and  one  was  born  dead  and  one  lived  but  six  days. 
The  mothers  were  kept  on  their  experimental  rations, 
and  the  following  year  they  repeated  in  all  essential 
details  the  reproduction  records  observed  in  the  first 
gestation  period. 

Records  were  kept  of  the  milk  production  during 
the  first  thirty  days  of  the  first  lactation  period.  The 
average  production  per  day  by  each  individual  in 
the  corn-fed  lot  was  24.03  pounds;  for  the  wheat- fed 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF        13 

animals  8.04  pounds,  and  for  the  oat-fed  animals 
19.38  pounds.  Those  fed  the  mixture  of  the  three 
plants  produced  19.82  pounds  of  milk  per  cow  per 
day  during  the  first  thirty  days.  In  the  second  lacta- 
tion period  the  figures  for  milk  production  were 
28.0;  16.1;  30.1;  21.3  pounds,  respectively,  per  day 
during  the  first  thirty  days. 

Through  autopsy  and  analysis  of  tissues  of  the 
young,  and  analysis  of  the  feces  and  urines  of  the 
animals  in  the  several  gi^oups,  an  elaborate  attempt 
was  made  to  solve  the  problem  of  the  cause  of  the 
marked  differentiation  of  the  animals  fed  these 
restricted  diets.  Interesting  data  were  seciu-ed 
which  showed  marked  differences  in  the  character 
of  the  fat  in  the  milk  of  cows  from  the  different  lots, 
and  the  observation  was  made  that  the  urines  of  the 
wheat  fed  animals  were  invariably  distinctly  acid 
in  reaction,  whereas  those  from  the  other  lots  were 
alkahne  or  neutral  to  fitmus  indicator.  It  was  not 
possible  by  any  means  knowTi  to  physiological  chem- 
istry, to  obtain  a  clue  to  the  cause  of  the  pronounced 
differences  in  the  physiological  well-being  of  the 
different  lots  of  cows.  This  experiment  confirmed 
the  author's  conviction  that  the  only  way  in  which 
the  problems  of  nutrition  could  ever  be  solved,  would 
be  to  solve  the  problem  of  the  successful  feeding  of 
the  most  simplified  diets  possible.  If  this  were 
accomphshed  it  would  be  possible  to  proceed  from 
the  simple  to  the  complex  diets  employed  in  prac- 
tical nutrition,  ascertaining  the  nature  of  the  dietary 


14      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

faults  in  each  of  the  natural  foods,  singly,  the  seed 
alone,  and  the  leaf  alone  before  attempting  to  inter- 
pret the  cause  of  malnutrition  in  animals  fed  the 
more  complex  mixtures. 

Such  an  undertaking  as  that  just  described,  viz., 
the  solution  of  the  problem  of  why  animals  do  not 
thinve  on  a  diet  of  purified  protein,  starch,  sugars, 
fats  and  inorganic  salts  which  contained  all  the 
elements  known  to  be  left,  as  ash,  on  the  incineration 
of  an  animal  body,  necessitated  the  employment  of 
small  laboratory  animals.  This  was  true  for  several 
reasons:  First,  because  it  is  difficult  and  laborious 
to  prepare  isolated  and  purified  food  substances  in 
sufficient  amounts  for  the  conduct  of  feeding  experi- 
ments; second,  it  is  both  necessary  and  desirable  to 
shorten  the  length  of  the  experiments  as  much  as 
possible,  consistent  with  obtaining  data  regarding 
growth  and  reproduction,  in  order  that  data  may 
accumulate  sufficiently  fast  to  make  progress  reason- 
ably rapid.  The  domestic  rat  seemed  to  be  the  most 
suitable  animal,  and  accordingly  it  was  selected. 
The  rat  has  a  gestation  period  of  but  21  days,  and 
the  young  are  ready  to  wean  at  the  age  of  25  days. 
The  female  usually  produces  her  first  litter  of  young 
at  the  age  of  about  120  days,  and  will  as  a  rule  have 
five  litters  by  the  time  she  reaches  the  age  of  four- 
teen months,  which  age  marks  the  end  of  her  fertihty. 
The  span  of  life  of  a  rat  which  is  well  nourished  is 
about  36  months.  A^Tien  such  an  animal  is  employed, 
it  is  possible  to  accomplish  within  a  relatively  short 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF        15 

time,  the  accumulation  of  data  regarding  growth 
and  reproduction  which  it  would  take  years  to  secure 
with  domestic  animals  of  large  size,  long  period  of 
gestation  and  long  span  of  life. 

A  sufficient  number  of  comparable  experiments 
have  now  been  conducted  with  several  species  of 
animals  to  make  it  appear  certain  that  the  chemical 
reciuirements  of  one  species  are  the  same  as  that  of 
another  among  all  the  liigher  anmials.  The  requu-e- 
ments  ^\dth  respect  to  the  physical  properties  of  the 
food  vary  gi^eatly.  The  ruminants  must  have  bulky 
food  with  the  right  consistency,  whereas  the  omnivora 
(man,  pig,  rat,  etc.),  cannot,  because  of  the  nature 
of  their  digestive  tracts,  consume  enough  of  such 
foods  as  leaves  and  coarse  vegetables,  to  meet  their 
energy  requirements. 

The  early  efforts  to  nourish  young  rats  on  diets 
composed  of  purified  proteins,  carbohydrates,  fats 
and  mineral  salts,  confirmed  the  results  of  the  earlier 
investigators.  The  animals  lived  no  longer  on  such 
food  mixtures,  than  when  allowed  to  fast.  The 
rations  employed  w^ere  of  such  a  character  that  the 
most  thorough  chemical  analysis  could  reveal  no 
reason  why  they  should  not  adequately  nourish  an 
animal.  It  seemed  obvious  that  there  was  some- 
thing lacking  from  such  mixtures  which  is  indis- 
pensable for  the  nutrition  of  an  animal,  and  a  system- 
atic effort  was  made  during  the  years  that  followed 
to  discover  the  cause  of  failure  of  animals  to  develop 
on  diets  of  purified  and  isolated  food-stuffs.    It  was 


16      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

not  until  1912  that  light  began  to  be  shed  upon  the 
problem. 

The  diet  which  was  most  in  use  at  that  time  con- 
sisted of  purified  casein  to  the  extent  of  about  18 
per  cent,  lactose  20  per  cent  (supposed  to  be  pure), 
about  5  per  cent  of  some  fat,  together  with  a  salt 
mixture  which  was  made  up  in  imitation  of  the  min- 
eral content  of  milk,  and  the  remainder  of  starch  to 
make  100  per  cent.^  This  food  mixture  was  sup- 
posed to  be  composed  of  materials  sufficiently  pure 
to  comply  with  the  requirements  of  such  work; 
that  is,  they  were  supposed  to  contain  too  little  of 
any  impurities  which  would  in  any  way  influence 
the  results.  With  this  diet  the  interesting  observa- 
tion was  made  that  growth  could  be  secured  when  the 
fat  in  the  food  mixture  was  butter  fat,  whereas  no  growth 
could  be  secured  when  the  butter  fat  was  replaced  by 
lard,  olive  oil  or  other  vegetable  oils.  Egg  yolk  fats 
were  next  tried  and  were  found  to  induce  growth  in 
the  same  manner  as  butter  fat.  It  was  definitely 
established  that,  contrary  to  the  past  beliefs,  the 
fats  are  not  all  of  the  same  dietary  value.  Certain 
fats  contain  some  substance  which  is  not  dispensable 
from  the  diet,  whereas  other  fats  do  not  contain  the 
dietary  essential  in  question. 

The  portion  of  the  food  mixture  other  than  fat, 
appeared  to  contain  only  substances  of  knowm  com- 
position, i.  e.,  protein,  carbohydrate  and  inorganic 
salts,  and  for  a  time  it  appeared  that  the  unknown 
substance  in  butter  fat  was  the  only  element  of 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       17 

myster}^  in  the  diet.  The  lactose  or  milk  sugar  was 
carefully  examined  as  to  its  purity  and  was  judged 
to  be  sufficiently  pure  to  be  satisfactory  for  such 
expermiental  work,  since  it  was  practically  free  from 
nitrogen.  The  tentative  conclusion  w^as  reached 
that  the  essential  factors  in  an  adequate  diet  included 
one  substance  or  a  group  of  substances  which  had 
not  been  appreciated  in  the  past,  and  that  these, 
if  there  should  be  more  than  one,  w^ere  associated 
with  certain  fats  but  not  with  all. 

This  observation  was  in  harmony  \vith  the  pub- 
lished work  of  Stepp  ^  which  had  appeared  in  1909. 
Stepp  observed  that  gro^^^l  mice  were  satisfactorily 
nourished  by  a  bread  which  was  made  with  milk, 
but  that  early  failure  and  death  followed  when  the 
animals  were  fed  the  same  bread  which  had  been 
previously  extracted  with  alcohol.  ^Mien  the  sub- 
stances extracted  from  the  bread  by  alcohol  were 
replaced,  the  bread  was  again  rendered  efficient  for 
the  maintenance  of  life  and  health.  He  demonstrated 
in  other  experiments  that  the  bread  could  be  ex- 
tracted with  ether  or  with  chloroform  ^\dthout  re- 
moving the  substance  wliich  was  soluble  in  alcohol, 
and  without  which  the  animals  steadily  failed. 
Stepp  considered  the  unknowm  substance  or  sub- 
stances with  which  he  was  dealing  in  his  feeding  work, 
as  belonging  to  the  not  well  defined  group  of  sub- 
stances generally  called  lipoids.  This  group  includes 
fats  and  related  substances  more  complex  in  char- 
acter, some  of  which  contain  the  elements,  phos- 


18    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

phorous  and  nitrogen.  Stepp  was  not  able  to  secure 
with  any  knowTi  lipoid,  the  effects  which  resulted 
from  the  administration  of  the  alcohol-soluble  por- 
tion of  his  milk  bread. 

A  new  viewpoint  was  suggested  by  F.  G.  Hopkins 
of  Cambridge,  England,  in  1912.^^  He  had  as  early 
as  1906  conducted  experiments  in  the  feeding  of  mix- 
tures of  purified  protein,  carbohydrate,  fats  and 
mineral  salts  and  was  aware  of  the  fact  that  neither 
maintenance  of  body  weight,  nor  growth  could  be 
secured  with  such  diets.  He  then  tried  the  addition 
of  such  amounts  of  milk  as  would  furnish  4  per  cent 
of  the  total  dry  matter  of  the  food  mixture  and  ob- 
served that  growth  could  proceed  when  such  milk 
additions  were  made.  Hopkins  suggested  the  exist- 
ence of  certain  unidentified  food  substances  which 
were  supplied  by  the  milk  and  to  these  he  gave  the 
name  '^accessory"  articles  of  the  diet. 

Attention  has  been  called  to  the  fact  that  Eijk- 
man,  a  student  of  the  disease,  beri-beri,  made  the 
discovery  in  1897  that  pigeons  fed  solely  upon  pol- 
ished rice,  develop  usually  within  three  or  four  weeks, 
a  state  of  paralysis  which  is  called  pol^meuritis,  and 
is  analogous  to  beri-beri  in  man.  He  found  that 
when  the  birds  were  given  the  entire  rice  kernel,  or 
unpolished  rice  the  disease  did  not  develop.  It  was 
found,  furthermore, that  the  administration  of  rice  pol- 
ishings  to  pigeons  suffering  from  polyneuritis,  caused 
prompt  relief  of  their  symptoms.  Eijkman's  ob- 
servations attracted  little  attention  until  1911,  when 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF        19 

Funk  took  up  the  study  of  beri-beri,  and  made  an 
elaborate  attempt  to  isolate  and  study  the  ''curative " 
substance  in  rice  pohshings.^^  Fraser  and  Stanton 
had,  however,  in  1907,  employed  alcohohc  extracts 
of  rice  polishings  for  the  relief  of  experunental 
poljTieuritis.^-  In  the  work  of  these  investigators 
the  erroneous  assumption  seems  to  have  prevailed 
that  the  process  of  pohshing  consists  essentially  of 
the  removal  of  the  outer  covering,  or  bran  layer  of 
the  rice  kernel.  As  a  matter  of  fact  the  rice  germ 
is  in  a  very  exposed  position,  and  is  easily  rubbed 
off  during  the  process  of  polishing.  As  was  later 
shown  by  ]\IcCollum  and  Da\4s,  for  the  wheat 
kernel,  the  germ  is  a  very  different  thing  from  the 
seed  from  the  dietary  standpoint. ^^  The  reason  for 
this  will  be  made  clear  later. 

The  studies  of  Eijkman,  Hopkins,  Fraser  and 
Stanton  and  Funk,  referred  to  above,  clearly  sug- 
gested that  there  was  required  in  the  diet  something 
other  than  protein,  carbohydrate,  fats  and  inorganic 
salts.  ^Alien  jNIcCollum  and  Davis  succeeded  in 
securing  growth  in  young  rats  fed  upon  a  mixture  of 
''purified"  food-stuffs,  when  the  mixture  contained 
butter  fat,  but  no  growth  when  vegetable  fats  or 
the  body  fats  of  animals  were  substituted,  it  appeared 
to  them  that  the  only  element  of  mystery  in  the  diet 
was  that  associated  with  certain  fats.  This  could 
not  at  first  be  harmonized  with  the  observation  of 
Funk,  namely,  that  butter  fat  had  no  favorable 
influence  on  pigeons  which  were  suffering  from  ex- 


20      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

perimental  beri-beri.^''  His  studies  seemed  to  in- 
dicate that  there  is  necessary  in  the  normal  diet  at 
least  one  other  substance,  the  absence  of  which 
brought  on  the  attack  of  polyneuritis.  Later  experi- 
ments by  McCollum  and  Davis  cleared  up  the  prob- 
lem, but  not  without  a  considerable  amount  of 
experimenting  and  delay. 

McCollum  and  Davis  arrived  at  the  conclusion 
that  aside  from  the  long  recognized  constituents  of 
the  normal  diet,  there  is  some  unknown  substance  in 
butter  fat  which  must  likewise  be  furnished  in  the 
food,  and  began  a  systematic  investigation  of  the 
problem  of  why  a  young  animal  cannot  grow  when 
restricted  to  a  single  grain  such  as  wheat,  maize 
(corn),  oats,  peas,  beans,  etc.  They  had  tried  many 
times  to  limit  young  rats  to  whole  wheat,  or  other 
grain  as  their  sole  food,  and  had  found  that  they 
not  only  failed  to  grow,  but  would  not  live  many 
weeks.  Chemical  analysis  shows  the  cereal  grains 
to  contain  all  the  essential  food  substances,  for  which 
we  know  how  to  analyze,  viz :  proteins,  starch,  sugar, 
fats  and  all  the  mineral  salts  which  occur  in  the  body 
of  an  animal. 

It  was  reasoned  that,  since  all  the  dietary  essen- 
tials, except  possibly  the  one  which  is  not  present  in 
vegetable  fats,  are  certainly  present  in  the  wheat 
kernel,  the  faults  in  the  latter  must  depend  upon  a 
lack  of  the  unknown  substance  contained  in  butter 
fat,  or  on  the  quality  of  some  one  or  more  of  the  well 
recognized    constituents    of    the    diet.      It    seemed 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       21 

possible  to  discover  by  means  of  a  systematic  series 
of  feeding  experiments  in  which  the  quahty  of  the 
seed  should  be  improved  with  respect  to  one  dietary 
factor  at  a  time,  which  factor  was  interfering  with 
growth.  Accordingly  the^^  fed  wheat  in  the  following 
combinations,  and  with  the  results  noted: 

(1)  WTieat  alone no  growth,  short  life. 

(2)  Wheat  plus  purified  protein no  growth,  short  life. 

(3)  Wheat  plus  a  salt  mixture  wliich  gave  it  a  mineral  content 

similar  to  that  of  milk very  little  growth. 

(4)  Wheat  plus  a  gro\\i:h  promoting  fat  (butter-fat) 

no  growth. 

From  these  results  it  seemed  apparent  that  either 
their  working  hypothesis  regarding  the  factors  which 
are  necessary  in  an  adequate  diet,  must  be  wrong, 
or  there  must  be  more  than  a  single  dietary  factor 
of  poor  quality,  and  jointly  responsible  for  the  poor 
nutrition  of  the  animals.  In  order  to  test  this  theory 
they  carried  out  another  series  of  feeding  experiments, 
in  which  wheat  was  fed,  supplemented  with  two 
purified  food  additions. 

(5)  Wheat  plus  protein,  plus  the  salt  mixture Good 

growth  for  a  time.     Few 
or  no  young.     Short  life. 

(6)  Wheat  plus  protein,  plus  a  growth-promoting  fat  (butter- 

fat)  No  growth.     Short  life. 

(7)  Wheat  plus  the  salt  mixture^  plus  the  growth-promoting  fat, 

(butter-fat) Fair  gi'owth  for  a  time.    Few 

or  no  young.     Short  life. 


22     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

The  behavior  of  the  animals  fed  wheat  with  two 
purified  food  additions  was  highly  suggestive  that 
there  are  three  dietary  factors  of  poor  quality  in 
the  whe^-t  kernel.  This  was  demonstrated  to  be 
true  by  a  feeding  trial  in  which  wheat  was  fed  with 
three  purified  food  additions: 

(8)  Wheat  plus  protein,  plus  the  salt  mixture,  plus  a  growth- 
promoting  fat  (butter-fat)  ....  Good    growth,    normal 

number  of  young,  good 
success  in  rearing  young; 
life  approximately  the 
normal  span. 

McCollum  and  Davis  were,  in  1912,  more  than 
ever  convinced  that  the  only  element  of  mystery  in 
the  normal  diet  was  the  unidentified  substance  in 
butter  fat,  for  with  the  improvement  of  three  dietary 
factors  wheat  became  a  satisfactory  food  for  the 
nutrition  of  an  animal  during  growth  and  for  the 
support  of  all  the  functions  of  reproduction  and 
rearing  of  young. 

This  series  of  experiments  brought  to  light  two 
new  viewpoints  in  animal  nutrition,  one  of  which  was, 
that  the  inorganic  content  of  the  wheat  kernel,  although 
it  furnishes  all  the  necessary  elements,  does  not  contain 
enough  of  certain  of  these  to  meet  the  requirements  of  a 
young  animal  during  the  growing  period.  It  is  true 
that  some  years  earlier  Henry,  ^^  had  called  at- 
tention to  the  deficiency  of  the  corn  kernel  in  ash 
constituents,  and  had  in  some  of  his  experiments 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       23 

added  wood  ashes  to  the  diet,  with  noticeable  im- 
provement in  the  well-being  of  the  animals.  The 
fact  that  seeds  such  as  wheat  fail  to  supply  enough 
of  any  of  the  essential  inorganic  elements  was  not 
geneially  appreciated  and  was  given  but  Httle  at- 
tention in  works  on  nutrition.  Later,  work  by  Mc- 
Collum  and  Simmonds,  demonstrated  that  the  de- 
ficiency in  mineral  elements  in  wheat  and  other 
seeds  is  limited  to  thi^ee  elements,  calcim,  sodium 
and  chlorine. 

A  second  new  viewpoint  brought  out  by  these  ex- 
periments was  the  fact  that  the  wheat  kernel  is  indeed 
too  poor  in  its  content  of  the  unidentified  substance 
which  butter  fat  contains,  to  satisfactorily  nourish  an 
animal  over  a  long  period  of  time. 

It  has  already  been  mentioned  that  the  studies  of 
Kossel,  Fischer  and  of  Osborne,  had  made  it  clear 
that  there  should  exist  very  pronounced  diffei'ences 
in  the  value  of  the  proteins  from  different  sources. 
The  proteins  were  prepared  in  a  state  of  relative 
purity  and  were  digested  in  the  laboratory  by  means 
of  acids,  and  were  analyzed  by  the  methods  of 
Fischer  and  of  Kossel.  Certain  of  the  eighteen  di- 
gestion products,  the  amino-acids,  were  determined 
quantitatively  sp  far  as  the  methods  would  permit. 
Although  the  methods  were  never  perfected  so  as  to 
give  results  which  w^ere  approximately  quantitative, 
except  in  the  case  of  less  than  a  third  of  the  amino- 
acids  which  were  known  to  be  formed  in  the  di- 
gestion of  proteins,  it  was  shown  in  the  case  of  these 


24     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

few  that  there  were  very  great  variations  in  the  pro- 
portions among  them  in  the  mixture  obtained  from 
proteins  from  different  som-ces.  Thus  the  proteins 
of  the  muscle  tissues  of  several  species  of  animals 
were  sho^^^l  to  yield  between  12  and  14  per  cent  of 
glutamic  acid,  one  of  the  digestion  products  obtained 
from  practically  all  proteins.  The  same  amino-acid 
is  present  in  the  two  principal  proteins  of  the  wheat 
kernel  to  the  extent  of  about  40  per  cent  of  the 
total  protein.  These  two  proteins  together  make 
about  85  per  cent  of  the  total  protein  of  the  wheat 
kernel.  Other  equally  great  differences  were  shown 
to  exist  in  the  composition  of  proteins  of  our  common 
food-stuffs  and  those  of  the  tissue  proteins  which 
are  formed  during  growth. 

A  good  illustration  of  the  problems  which  the 
animal  meets  in  its  protein  nutrition,  may  be  had  by 
comparing  the  digestion  products  of  the  protein 
molecule  to  the  letters  of  the  alphabet.  The  pro- 
teins of  the  food  and  of  the  tissues  are  made  up 
of  the  same  letters  arranged  in  different  orders  and 
present  in  different  proportions.  In  growth  the 
animal  takes  as  food,  proteins  which  are  very  unlike 
those  of  its  tissues,  digests  these  into  the  simple  com- 
plexes, the  amino-acids,  and  then,  after  absorbing 
these,  puts  together  the  fragments  in  new  order, 
and  in  new  proportions  to  form  the  tissue  proteins. 

If  the  muscle  tissue  of  an  animal  be  likened  to  a 
block  of  printer's  type  so  arranged  as  to  print  the 
rhyme  beginning  ''Jack  Spratt,  who  could  eat  no 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       25 

fat,  and  his  wife  could  eat  no  lean,"  the  proteins  of 
which  the  muscle  consists  are  represented  by  the 
mdividual  words,  and  the  digestion  products  of  the 
proteins  by  the  letters  of  which  the  words  consist. 
Now  if  the  aniinal  could  take  in  its  food  proteins 
which  correspond  to  a  block  of  type  which  would 
print  the  jingle  beginning:  ''Peter  Piper  picked  a 
peck  of  pickled  peppers,"  it  is  easy  to  understand 
that  when  the  proteins  of  the  food  are  resolved  to 
their  constituent  letters,  and  an  effori  made  to  form 
the  body  proteins  of  the  new  and  different  t^'-pe 
from  the  letters  supplied  by  the  food,  the  trans- 
formation cannot  be  made.  In  setting  up  the  first 
line,  '"'Jack  Spratt  could  eat  no  fat  and  his  wife 
could  eat  no  lean/' we  need  four  of  the  letter  t,  but 
the  food  proteins  contain  but  one.  The  first  line  of 
the  Jack  Spratt  rhyme,  which  represents  the  muscle 
proteins,  requires  but  one  letter  p,  whereas  the  food 
proteins  represented  by  the  Peter  Piper  rhyme 
yield  nine  in  the  first  line.  The  first  line  of  the 
Jack  Spratt  rhyme  contains  the  letters  j  and  n, 
whereas  the  Peter  Piper  rhyme  contains  none,  so 
that  even  with  the  entire  stanza: 

Peter  Piper  picked  a  peck  of  pickled  peppers 
If  Peter  Piper  picked  a  peck  of  pickled  peppers, 
Where's  the  peck  of  pickled  peppers, 
That  Peter  Piper  picked? 

it  is  not  possible  to  reproduce  even  the  first  line  of 
the  Jack  Spratt  rhyme,  and  in  order  that  gi'owth 


26     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

might  become  possible,  it  would  be  necessary  to 
take  proteins  of  another  character,  which  would 
supply  the  missing  letters. 

Such  a  comparison  between  food  proteins  and 
tissue  proteins  gives  a  good  illustration  of  the  kind 
of  problem  which  the  animal  meets  in  its  protein 
nutrition.  The  most  conspicuous  protein  of  the  corn 
kernel  (zein)  is  wholly  lacldng  in  tlu-ee  of  the  amino- 
acids  or  digestion  products  which  are  obtainable 
from  most  tissue  proteins.  In  accord  with  what  we 
should  expect  on  theoretical  grounds,  this  protein 
is,  when  taken  as  the  sole  source  of  amino-acids,  not 
capable  of  supporting  growth,  or  of  maintaining  an 
animal  in  body  weights  This  illustration  shows  how 
we  m.ay  have  excellent,  good  or  poor  food  proteins 
for  the  formation  of  body  proteins  in  gi^owth. 

The  investigations  described  above,  the  object  of 
which  was  to  find  the  cause  of  the  failure  of  an 
anmial  to  grow  when  restricted  to  wheat  as  its  sole 
source  of  nutriment,  w^ere  carried  out  in  1912,  the 
year  following  the  publication  of  the  first  work  by 
Funk  on  polyneuritis.  In  the  same  year  Hop- 
kins called  attention  to  the  remaiivable  effects  pro- 
duced by  the  addition  of  small  amounts  of  milk  to 
diets  composed  of  purified  food-stufTs.  The  'Sdta- 
mine''  hypothesis  had  just  been  formulated  by 
Funk.i*^  McCoUum  and  Davis  were,  therefore,  aware 
of  the  relation  of  a  diet  of  polished  rice  to  experi- 
mental beri-beri.  They  believed,  in  the  light  of 
their  experiences  with  the  diet  of  purified  protein, 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       27 

carbohydrate,  fats  and  inorganic  salts,  which,  they 
observed,  was  capable  of  inducing  growth  when  cer- 
tain fats  were  supplied,  but  not  when  others  were 
substituted,  and  the-  further  fact  that  wheat  could 
be  supplemented  by  purified  protein,  a  growth- 
promoting  fat,  and  a  suitable  salt  mixture,  i.  e.  with 
food-stuffs  of  knowTi  character,  that  there  was  but 
a  single  unidentified  substance  necessaiy  in  the  diet. 
They  decided  to  next  apply  to  polished  rice  the 
same  procedure  which  had  shown  so  clearly  the 
nature  of  the  dietary  deficiencies  of  wheat.  Rice, 
thcA^  reasoned,  could  be  nothing  less  than  a  mixture 
of  proteins,  starch,  traces  of  fat,  and  a  mixture  of 
inorganic  salts,  similar  to  that  contained  in  wheat, 
but  smaller  in  amount.  It  should,  therefore,  be 
supplemented  ^^dth  a  suitable  salfc  mixture,  a  purified 
protein,  and  a  growth-promoting  fat,  so  as  to  in- 
duce gi'owth  and  maintain  animals  for  a  long  time 
in  a  state  of  health.  This  seem.ed  to  be  a  necessaiy 
conclusion,  since  they  had  secured  growth  and  well- 
being  in  animals  fed  strictly  upon  a  mixtme  of  puii- 
fied  protein  (casein),  starch,  milk-sugar,  butter  fat 
and  a  mixture  of  inorganic  salts  of  suitable  com- 
position. 

It  was  a  great  surprise  to  jMcColIum  and  Davis 
to  find  that  polished  rice,  even  when  supplemented 
with  the  purified  protein,  casein,  butter  fat  and  a 
salt  mixture  properly  constituted,  failed  utterly  to 
induce  any  growth  in  young  rats.^^  Not  only  did 
they  fail  to  grow,  but  in  the  course  of  a  few  weeks 


28      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

they  developed  in  some  cases  a  state  of  paralysis 
which  was  suggestive  of  polyneuritis.  Here  was  an 
apparent  contradiction.  The  poUshed  rice  could  be 
nothing  less  than  a  mixture  of  protein,  carbohydrate 
and  salts.  The  only  difference  between  this  and  the 
mixture  of  supposedly  purified  food-stuffs  with  which 
they  had  achieved  success  was  in  the  20  per  cent  of 
milk  sugar  w^hich  the  latter  contained.  It  was, 
therefore,  decided  to  repeat  the  experiments  with 
the  latter  mixture,  with  the  milk  sugar  replaced  by 
starch.  It  was  found  that  this  change  in  the  com- 
position of  the  food  mixture  made  the  difference  be- 
tween success  and  failure.  No  growth  could  be  se- 
cured w^hen  the  milk  sugar  was  omitted.  Later 
experiments  showed  that  if  milk  sugar  was  suf- 
ficiently purified  by  repeated  crystallization  it  was 
no  longer  effective  in  inducing  gi'owth  w^hen  added 
to  the  purified  food  mixture,  whereas  the  water  from 
which  the  sugar  had  been  crystalHzed  would,  w^hen 
evaporated  upon  the  food  mixture,  render  it  capable 
of  inducing  growth.  This  made  it  evident  that  there 
is  indeed  a  second  dietary  essential,  of  which  an 
animal  needs  but  a  very  small  amount,  but  which 
is  absolutely  necessaiy  for  both  growth  in  the  young 
and  the  maintenance  of  health  in  the  adult. 

FuHher  experiments  were  then  conducted  to  find 
whether  this  unidentified  substance  which  w^as  being 
added  accidentally  as  an  impurity  in  the  milk  sugar, 
was  the  same  as  the  substance  which  Fraser  and 
Sta:  ton  and  Funk  were  dealing  with  in  their  studies 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       29 

of  beri-beri.  It  was  found  that  pigeons  which  had 
developed  beri-beri  as  the  result  of  being  fed  ex- 
clusively upon  polished  rice,  could  be  temporarily 
''cured"  with  any  preparation  which  would,  when 
added  to  the  diet  of  purified  food-stuffs,  containing 
a  gi'owth-promoting  fat,  cause  animals  to  gi'ow. 

Follo^^'ing  the  method  introduced  by  Fraser  and 
Stanton,  ]\IcCollum  and  Davis,  ^^  next  employed 
alcoholic  extracts  of  various  natural  foods,  adding 
the  alcohol  soluble  matter  to  the  standard  mixture 
of  purified  protein  (casein),  starch  (dextrinized), 
salts  and  butter  fat,  and  soon  became  con^dnced 
that  the  substance  which  relieves  the  condition  of 
pol>Tieuritis  in  pigeons  was  always  present  in  the 
preparations  wliich  render  the  purified  food  mixture 
capable  of  promoting  growth.  They  finally  adopted 
an  alcoholic  extract  of  wheat  germ  as  a  source  of 
this  dietary  factor  in  their  investigations.  Funk 
and  his  co-workers  had  previously  shown  that  the 
curative  substance  is  present  in  many  natural 
foods. ^^  Repeated  trials  showed  that  the  inclusion 
of  the  alcoholic  extract  of  wheat  germ  or  of  other 
food,  was  not  sufficient  to  induce  growth  unless 
the  butter  fat  was  likewise  added  to  the  purified  food 
mixture.  Both  the  growth-proinoting  fat  and  the 
trace  of  unidentified  substance  in  the  alcoholic  extract 
of  wheat  germ  are  necessary  for  the  promotion  of 
growth  or  the  preservation  of  health. 

It  has  been  pointed  out  that  Funk,  in  his  examina- 
tion of  the  vai'ious  natural  foods  for  the  purpose  of 


30     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

determining  the  distribution  of  the  antineuritic  sub- 
stance (substance  which  reUeves  polyneuritis)  found 
butter  fat  ineffective.  This  was  later  confirmed  by 
McCollum  and  Kennedy. ^^ 

Through  the  '^vitamine"  hypothesis,  Funk  at- 
tempted to  account  for  the  diseases  beri-beri,  scurvy, 
pellagra  and  rickets,  as  being  each  due  to  the  lack 
of  a  specific  chemical  substance,  a  ''vitamine,"  in 
the  diet.^^  This  was  a  very  logical  conclusion  from 
the  data  available  to  Funk.  Scurvy,  it  had  long 
been  known  is  relieved  in  a  very  spectacular  manner 
by  the  inclusion  of  fresh  vegetables  or  orange  juice 
in  the  diet,  and  there  was  no  doubt  that  the  disease 
developed  as  the  result  of  a  diet  of  poor  quality.  On 
first  consideration  it  seemed  very  reasonable  to 
assume  that  there  is  an  ''antiscorbutic  vitamine'^ 
in  certain  fruits  and  vegetables. 

Pellagra  has  long  been  suspected  of  being  due  to 
faulty  diet,  although  the  exact  manner  in  which  the 
diet  is  unsatisfactoiy  remained  obscure.  It  was 
generally  appreciated  by  clinicians  that  a  change  to 
a  highly  nutritious  diet  in  which  milk  and  eggs  were 
conspicuous  was  the  best  prophylactic  measure  for 
the  treatment  of  the  disease,  and  that  without  diet- 
ary measures,  all  remedies  fail.  It  was  not  surpris- 
ing that  Funk  should  have  regarded  pellagia  as  one 
of  the  ''deficiency"  diseases,  due  to  lack  of  a  "vita- 
mine"  in  the  diet.  As  will  be  shown  later  (Chapter  V) 
there  has  since  been  secured  much  experimental  evi- 
dence in  support  of  the  view  that  scurvy  and  pellagra 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       31 

do  not  arise  from  deficiency  in  the  diet  of  specific 
chemical  substances  in  the  sense  in  which  Funk 
suggested.  This  seems  to  be  true  also  of  rickets. 
In  view  of  the  considerations  just  mentioned  rel- 
ative to  the  cause  of  scurvy  and  pellagra,  and  the 
convincing  evidence  that  beri-beri  is  actually  caused 
by  specific  starvation  for  a  substance,  "\dtamine," 
as  Funk  suggested,  McCollum  and  Davis  formulated 
in  the  following  way,  their  working  hypothesis  as  to 
w^hat  constitutes  an  adequate  diet.  The  diet  must 
contain,  in  addition  to  the  long  recognized  dietary 
factors,  viz:  protein,  a  source  of  energy  in  the  form 
of  proteins,  carbohydrates  and  fats;  a  suitable  supply 
of  certain  inorganic  salts,  two  as  yet  unidentified 
substances  or  groups  of  substances.  ^^  One  of  these 
is  associated  with  certain  fats,  and  is  especially 
abundant  in  butter  fat,  egg  yolk  fats  and  the  fats 
of  the  glandular  organs  such  as  the  hver  and  kidney, 
but  is  not  found  in  any  fats  or  oils  of  vegetable  origin. 
The  second  substance  or  group  of  substances  of 
chemically  unidentified  nature,  is  never  associated 
with  fats  or  oils  of  either  animal  or  vegetable  origin. 
It  is  widely  distributed  in  natural  foods,  and  can  be 
isolated  in  a  concentrated,  but  not  in  a  pure  form, 
from  natural  food-stuffs  by  extraction  of  the  latter 
with  either  water  or  alcohol.  This  water  or  alcohohc 
extract  always  contains  the  substance  which  cures 
pol}meuritis.  At  the  time  it  seemed  possible  that 
it  also  contained  several  other  ''vitamines,"  pro- 
tective against  the  other  diseases  mentioned.    The 


32     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

former  substance  or  group  of  substances,  which  is 
associated  with  certain  fats  is  not  '^curative"  for 
any  of  the  Ust  of  diseases  which  Funk  designated  as 
'^vitamine"  deficiency  diseases.  Indeed,  butter  fat, 
which  is  the  food  containing  one  of  the  indispensable 
substances  in  greatest  abundance,  was  stated  by 
Funk  to  contain  no  ^^vitamine."  ^^ 

Nomenclature  of  the  Unidentified  Dietary  Essen- 
tials.— The  ending  amine  has  a  definite  and  specific 
meaning  in  organic  chemistry,  and  apphes  only  to 
substances  containing  the  element  nitrogen.  Since 
butter  fat,  which  is  very  rich  in  one  of  the  dietary 
essentials  in  question  is  practically,  if  not  entirely, 
free  from  nitrogen,  it  seems  almost  certain  that  the 
physiologically  indispensable  substance  which  it  con- 
tains is  free  from  nitrogen,  and  could  not  with  pro- 
priety be  designated  by  any  name  ending  in  amine. 
For  this  reason,  and  because  it  is  possible  to  divide 
the  unidentified  constituents  of  the  normal  diet  into 
two  classes  on  the  basis  of  their  solubility,  McCollum 
and  Kennedy  ^^  proposed  the  terms  fat-soluble  A 
and  water-soluble  B  to  designate  them.  The  former 
prevents  the  development  of  a  pathological  condition 
of  the  eyes,^^  the  latter  prevents  the  development  of 
beri-beri.  As  will  be  shown  later,  there  is  much 
evidence  for  and  none  against  the  view  that  what  we 
designate  by  each  of  these  terms  is  in  reality  but  a 
single  physiologically  indispensable  substance  and 
not  a  group  of  substances.  This  necessitates  the 
further  assumption  that  certain  of  the  diseases  of 


BIOLOGICAL  ANALYSIS  OF  FOOD-STUFF       33 

dietary  origin,  which  Funk  held  to  be  due  to  ^^vi- 
taniine"  starvation,  are  in  reahty  due  to  other  causes. 
This  view  will  be  supported  by  further  evidence  later. 
Indeed  it  is  not  possible  to  longer  regard  scurvy  as 
a  ^'vitaniine"  deficiency  disease. 

The  ^Sdtamine"  hypothesis  of  Funk  was  extremely 
attractive  and  seemed  to  account  for  the  etiology 
of  several  diseases  in  a  most  satisfactory  way.  It 
seemed  to  rest  upon  sound  observations,  but  in 
reality  it  rested  only  upon  suggestive  chemical  ev- 
idence. It  failed  to  stand  the  test  of  a  systematic 
investigation  of  all  the  more  important  natural 
food-stuffs,  by  the  biological  method  which  was 
described  in  its  essential  features  in  illustrating  the 
nature  of  the  dietary  deficiencies  of  the  wheat  kernel. 


CHAPTER  II 

EXPERIMENTAL  SCURVY  AND  THE  DIETARY  PROPERTIES 

OF   VEGETABLES 

McCollum,  Simmonds  and  Pitz  ^  sought  to  test 
the  vaUdity  of  the  ''vitamine"  hypothesis  in  its 
relation  to  scurvy,  by  an  indirect  method.  The  next 
logical  step  in  the  investigation  of  the  possible  num- 
ber of  dietary  essentials  of  unknown  chemical  nature 
which  occur  in  the  growth-promoting  fats  (fat- 
soluble  A),  and  in  the  preparations  which  are  never 
associated  with  fats  (water-soluble  B),  seemed  to  be 
to  study  the  oat  kernel.  There  seemed  much  reason 
to  beUeve  that  this  seed  would  prove  to  be  unique 
among  the  ordinary  seeds  in  its  dietary  properties. 
Theobald  Smith  ^  had,  in  1895,  called  attention  to  the 
fact  that  a  diet  of  oats  would  cause  in  guinea  pigs 
the  development  of  a  condition  suggestive  of  scurvy. 
In  1909  Hoist  and  his  co-workers  in  Sweden  ^  de- 
scribed numerous  experiments  involving  the  produc- 
tion and  relief  of  experimental  scurvy  in  the  guinea 
pig.  Hoist  observed  that  when  this  animal  is  re- 
stricted to  a  diet  of  oats  it  rarely  fails  to  develop 
scurvy  within  a  few  weeks.  The  disease  which  is  so 
produced  is  strikingly  suggestive  of  scurvy  in  man. 
There  is  pronounced  swelling  of  the  knee  and  elbow 
joints,  with  rupture  of  the  capillaries  at  these  sites, 

34 


DIETARY  PROPERTIES  OF  VEGETABLES       35 

and  there  is  also  a  spongy  and  hemorrhagic  condition 
of  the  gums. 

Hoist  stated  that  the  disease  was  due  to  a  deficiency 
of  the  oat  kernel  in  an  antiscorbutic  substance,  which 
is  relatively  unstable  when  manipulated  in  the  lab- 
oratory. Milk  was  stated  to  be  efficient  for  the  cure 
of  the  disease  induced  by  an  oat  diet,  provided  it  was 
raw  or  had  not  been  heated  to  very  high  tempera- 
tures. ]\Iilk  wliich  had  been  heated  to  90°  C.  for 
ten  minutes  was  said  to  be  still  effective,  but  boiled 
milk  failed  to  induce  a  cure.  Raw  cabbage  was 
stated  to  be  highly  efficient  as  a  remedy  against 
the  disease  in  the  guinea  pig,  whereas  cooked  or 
dried  cabbage  had  lost  most  of  its  antiscorbutic 
property. 

In  view  of  these  observations,  it  seemed  that,  if 
it  were  true  that  scur\^  is  as  Funk  and  Hoist  be- 
lieved, a  disease  resulting  from  ^^vitamine"  defi- 
ciency, the  oat  kernel  should  prove  to  be  a  natural 
food-stuff  v/hich  lacked  the  antiscorbutic  '' vitamine" 
but  contained  the  anti-beri-bei  i,  and  perhaps,  also, 
the  anti-pellagra  and  ot her '  ^  vitamines. ' '  McCollum, 
Smmaonds  and  Pitz^  submitted  the  oat  kernel  to  the 
systematic  procedure  of  the  biological  method  of 
analysis,  feeding  it  as  the  sole  source  of  nutriment, 
and  also  with  single  and  multiple  additions  of  purified 
food  substances,  employing  the  rat  as  the  experi- 
m^ental  anhnal.  This  showed  that  the  oat  kernel 
(rolled  oats)  can  be  supplemented  by  the  addition  of 
a  salt  mixture  of  appropriate  composition,  a  growth- 


36      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

promoting  fat,  and  the  purified  protein  gelatin,  so  as 
to  induce  growth  at  the  maximum  rate  in  young  rats 
from  weaning  time  to  the  full  adult  size,  and  sup- 
ported the  production  of  a  few  young.  WTien  any 
one  of  these  additions  is  omitted,  the  animals  fail  to 
develop. 

The  oat  kernel,  therefore,  contains  all  the  dietary 
essentials  in  bhe  water-soluble  group  (provided  there 
is  more  than  one  such  substance).  Like  wheat  it 
lacks  a  sufficient  amount  of  the  fat- soluble  A  to 
support  noi'mal  nutrition.  It  was  impossible  to 
harmonize  the  results  described  by  Hoist  in  the 
production  of  experimental  scurvy  in  the  guinea  pig 
with  those  of  McCollum,  Sinamonds  and  Pitz,  in 
which  the  rat  served  as  the  experimental  animal, 
without  making  assumptions  which  would  gi^eatly 
compUcate  the  w^hole  subject  of  nutrition  investiga- 
tions. There  were  serious  discrepancies  in  the  ex- 
perimental data  from  different  sources.  Hoist's 
studies  pointed  to  the  existence  in  the  normal  diet 
of  a  substance  or  substances  of  unknown  character, 
which  were  easily  destroyed  by  heat  or  by  dessica- 
tion,  and  which  act  as  protective  agents  against 
scurvy  in  the  guinea  pig,  and  appeared  to  demon- 
strate that  the  supposed  antiscorbutic  substance  or 
substances  w^ere  absent  from  the  oat  kernel.  The 
studies  with  the  rat  demonstrated  beyond  con- 
troversy, that  at  least  for  the  rat,  the  oat  kernel  is 
deficient  as  a  food  only  as  respects  the  factors,  in- 
organic salts,  fat-soluble  A,  and  in  a  lesser  degree  in 


DIETARY  PROPERTIES   OF  VEGETABLES       37 

the  quality  of  its  protein.  When  these  factors  are 
corrected,  the  oat  kernel  becomes  a  complete  food 
for  this  species. 

Scurvy  has  been  produced  experimentally  by 
faulty  diet  in  the  guinea  pig,  and  is  not  known  to 
occur  in  any  species  other  than  man  and  the  guinea 
pig.  If  the  explanation  of  Hoist  and  of  Funk  is  cor- 
rect that  scur\y  is  the  result  of  the  lack  of  a  specific 
substance  in  the  diet,  it  becomes  necessary  to  make 
the  further  assumption  that  man  and  the  guinea  pig 
require  this  substance,  since  both  suffer  from  the 
disease,  whereas  other  species,  as  the  rat,  do  not  re- 
quire this  complex  as  a  dietary  component.  The 
only  alternative  is  to  conclude  that  scur\^  is  in 
realty  not  a  ''deficiency"  disease  in  the  sense  in 
which  Funk  and  Hoist  employed  the  term.  That 
there  is  actually  no  such  unstable  ''antiscorbutic 
substance"  or  "antiscorbutic  vitamine"  as  postu- 
lated by  Hoist  and  Funk,  has  been  demonstrated  by 
the  studies  of  IMcCollum  and  Pitz.^  The  proof  of 
this  is  given  m  Chapter  V.  In  the  same  chapter  will 
be  discussed  the  other  so-called  ''vitamine"  deficiency 
diseases,  pellagTa  and  rickets,  and  the  character  of 
the  diets  which  play  a  part  in  their  etiology.  The 
data  available  supports  the  view  that  among  the  hst 
of  so-called  "  deficiency "  diseases,  beii-beri,  scur\^^ 
pellagra  and  rickets,  only  the  first  is  due  to  the  lack 
of  a  specific  protective  substance,  Funk's  "vitamine," 
or  water-soluble  B  in  the  diet.  The  others  are  at 
least  in  some  degree  the  result  of  faulty  diets,  but  not 


38      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

in  the  sense  in  which  Funk  and  Hoist  employed  the 
term  ^'deficiency."  McCollum  and  Simmonds  have 
pointed  out,  however,  that  in  the  pathological  con- 
dition of  the  eyes,  known  as  xerophthalmia,  of  dietary 
origin  mentioned  above,  we  have  a  second  deficiency 
disease,  analogous  to  beri-beri.^  All  the  facts  at 
present  available  point,  therefore,  to  the  beUef  that 
what  McCollum  and  his  co-workers  term  water- 
soluble  B,  is  in  reality  but  a  single  physiologically 
indispensable  substance.^  There  is  no  evidence  in 
support  of  the  \dew  that  the  term  fat -soluble  A  need 
be  considered  as  applying  to  more  than  a  single 
chemical  substance.  Xeropthalmia  of  dietary  origin 
will  be  described  later  (Chapter  V). 

Similarity  of  the  Seeds  from  the  Dietary  Standpoint. 
— By  the  application  of  the  biological  method 
of  analysis  of  a  food-stuff  to  each  of  the  more  im- 
portant seeds  employed  in  the  nutrition  of  man  and 
anim.als,  the  fact  w^as  brought  to  fight  that,  they  all 
resemble  each  other  very  closely  in  their  dietary 
properties.  The  list  of  seeds  examined  included, — 
wheat,^  corn,^  rice,^^  rolled  oats,  rye,^  barley,^  kaffir 
corn,^  millet  seed,^^  flaxseed, ^^  pea^^  and  both  the 
navy^^  and  the  soy  bean.^  These  all  contain  proteins 
which  are  of  distinctly  lower  biological  value  for 
growth  than  are  the  proteins  of  milk ;  they  all  are  too 
poor  in  the  same  three  inorganic  elements,  calcium, 
sodium  and  chlorine.  All  are,  with  the  exception  of 
millet  seed,  below  the  optimum  in  their  content  of 
the  dietary  factor,  fat-soluble  A.    These  three  diet- 


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DIETARY  PROPERTIES  OF  VEGETABLES      39 

ary  factors  must  be  improved  before  any  one  of  these 
seeds  becomes  complete  from  the  dietary  stand- 
point. The  seeds  are,  therefore,  to  be  classed  to- 
gether as  regards  their  food  values. 

Since  the  seeds  have  the  same  faults  from  the  diet- 
ary standpoint,  it  is  to  be  expected  that  when  fed  in 
mixtures  they  should  not  supplement  each  other  ex- 
cept as  regards  the  protein  moiety.  It  would  hardly 
be  expected  that  the  proteins  of  two  or  more  kinds 
of  seeds  should  be  deficient  in  the  same  amino-acids, 
and  in  the  same  degree,  and  feeding  trials  have  shoAMi 
that  mixtures  of  seeds  furnish  better  protein  values 
for  growth  than  do  the  single  seeds  when  fed  alone, 
properly  supplemented  with  respect  to  all  other 
factors.  From  the  similarity  of  the  inorganic  con- 
tent of  all  seeds,  and  their  low  content  of  the  fat- 
soluble  A,  it  should  be  necessary  to  supplement  any 
mixture  of  seeds  with  respect  to  both  these  factors 
.before  good  nutrition  can  be  secured.  Experimental 
trial  shows  this  to  be  the  case.  It  is  not,  therefore, 
possible  to  secure  appreciable  growth  in  young  animals 
fed  exclusively  upon  seed  products  as  the  sole  source  of 
nutriment. 

Casual  observation  teaches  us  that  such  animals 
as  the  ox,  horse,  sheep  and  goat  can  grow  and  live 
for  years  in  a  vigorous  condition  on  diets  derived 
entirely  from  vegetable  sources.  After  having  un- 
successfully attempted  numerous  times  to  induce 
growth  in  animals  fed  strictly  upon  seed  mixtures, 
the  thought  naturally  arose  tliat  there  must  be  some 


40      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

special  properties  in  the  leaves  of  the  plant  which 
cause  them  to  make  good  the  dietary  deficiencies  of 
the  seeds.  A  careful  inquiry  in  every  possible  direc- 
tion failed  to  discover  any  animal  which  in  its  natu- 
ral state  limits  its  diet  strictly  to  seeds.  Birds  all 
appear  to  vary  theii'  diet  of  seeds  with  insects  and 
worms,  and  most  birds  eat  to  some  extent  of  fruits 
and  certain  tender  leaves.  All  birds  probably  eat  a 
considerable  amount  of  mineral  substance  in  the 
form  of  particles  which  they  deliberately  swallow, 
and  they  secure  in  their  natural  state  more  or  less  of 
all  of  the  essential  mineral  elements  in  the  drinking 
water  which  has  permeated  the  ground.  These  sup- 
plemental sources  of  certain  food  substances,  which 
one  is  at  first  inclined  to  overlook,  or  if  considered, 
to  regard  as  of  an  accessory  nature,  and  therefore, 
if  '^accessory,"  dispensable,  are  in  reality  of  such 
importance,  that  it  is  not  too  much  to  say  that  the 
preservation  of  the  species  might  turn  upon  the 
opportunity  or  lack  of  opportunity  to  secure  these 
substances. 

Among  the  omnivora,  the  author  has  been  unable 
to  discover  any  species  which  subsists  entu^ely  upon 
seeds.  The  hog  is  a  typical  omniverous  feeder,  but 
it  is  well  knowTi  to  animal  husbandrymen  that  there 
are  but  two  successful  methods  of  pork  production, 
one  of  w^hich  is  to  feed  growing  pigs  on  grain  while 
they  have  access  to  a  good  pasture;  the  other  is  to 
feed  them  milk,  skim  milk,  or  butter-milk,  along 
with  a  grain  mixture.    Ignorance  of  this  fact  has  re- 


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DIETARY  PROPERTIES  OF  \^GETABLES       41 

suited  in  enormous  econoixdc  loss  to  farmers  who 
have  attempted  to  keep  growing  pigs  in  a  dry  lot 
and  feed  them  cereal  grains  and  by-products  derived 
from  these,  as  the  sole  source  of  nutriment.  Little 
gi'owth  can  be  secured  under  these  chcmiistances, 
and  the  reason  becomes  clear  from  what  has  been 
said  above  concerning  the  nature  of  the  dietary 
deficiencies  of  the  seeds  and  the  similarity  of  the 
seeds  from  the  dietary  standpoint.* 

It  was  a  great  surprise  to  ]\IcCollum,  Simmonds 
and  Pitz  ^-  to  find  that  appropriate  mixtures  of  leaf 
and  seed  make  fairly  satisfactory  food  mixtures  for 
the  support  of  growth,  whereas,  as  has  been  stated, 
they  were  unable  to  secure  any  appreciable  growth 
in  animals  fed  exclusively  on  seeds  and  seed  products, 
the  drinking  water  supphed  being  distilled  and  there- 
fore salt  free.  The  fii'st  leaf  which  was  studied  was 
that  of  the  alfalfa  plant,  for  the  reason  that  the 
ground,  mmiature  alfalfa  plant  is  extensively^  mar- 
keted as  a  supplementaiy  feed  for  pigs,  and  tlii'ough 
the  courtesy  of  the  Petei^  ^lilhng  Company  of 
Omaha,  Nebraska  a  product  ^'alfaha  flour''  was 
made  available  in  a  convenient  form.    This  consists 

*  It  Ls  not  to  be  understood  from  tliis  that  it  is  intended  to  imply 
that  no  increase  in  body  weight  can  be  secured  in  hogs  when  they  are 
confined  strictly  to  grain  mixtures.  They  may  indeed  become  very 
fat,  and  therefore  apparently  grow  for  a  time  on  such  foods  as  corn 
alone.  Even  under  farm  conditions,  where  they  are  able  to  secure 
a  supplementary  mineral  supply  through  the  water  they  drink  and 
through  the  consumption  of  soil  with  the  grain,  there  is  httle  growth 
in  the  sense  that  the  muscle  and  organ  tissues  increase  in  volume. 


42      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

of  the  dry,  immature  leaf  of  the  plant  ground  to  a 
very  fine  powder  of  a  bright  green  color. 

A  series  of  diets  consisting  of  seed,  60  per  cent, 
and  of  alfalfa  leaf  flour,  40  per  cent,  were  first 
fed  to  growing  rats.  The  seeds  employed,  included 
wheat,  corn,  rolled  oat,  rye,  millet  seed,  kaffir  corn, 
pea  and  bean.  The  degree  of  success  in  inducing 
growth  with  most  of  these  simple  mixtures  of  one 
seed  with  the  alfalfa  leaf  is  much  greater  than  can  ever 
be  secured  with  even  such  complex  mixtures  of  seeds 
as  corn,  wheat,  oat,  hemp  seed  and  millet  seed  in 
equal  proportions.  The  latter  mixture  can  support 
a  fair  amount  of  growth  when  its  inorganic  defi- 
ciencies are  made  good,  but  without  mineral  addi- 
tions almost  no  growth  can  be  secured.  Chart  6 
shows  typical  growth  curves  which  give  an  accurate 
idea  of  the  relative  values  for  growth  of  several 
combinations  of  the  alfalfa  leaf  with  seeds.  Among 
the  seeds  with  which  studies  have  been  made,  the 
oat  is  best  supplemented  by  the  alfalfa  leaf.  A 
simple  mixture  of  rolled  oats,  60  per  cent,  and  alfalfa 
leaf,  40  per  cent,  induces  nearly  normal  growth  to 
the  adult  size  in  the  rat  and  induces  a  fair  amount 
of  reproduction  and  rearing  of  young.  However, 
the  animals  fall  considerably  below  the  maximum 
performance  in  both  these  respects. 

An  examination  of  other  leaves  of  plants  showed 
that  the  latter  can  in  a  general  way  be  classed  to- 
gether as  food-stuffs  of  similar  character,  since  they 
resemble  each  other  more  or  less  closely,  just  as  the 


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DIETARY  PROPERTIES  OF  ^^GETABLES   43 

seeds  all  resemble  each  other  in  their  dietary  prop- 
erties. The  leaf  proves  to  be  a  very  differenfc  thing 
from  the  seed  from  the  dietary  standpoint.  The  dry 
leaf  usually  contains  from  three  to  five  times  as 
much  total  ash  constituents  as  does  the  seed,  and 
is  always  especially  rich  in  just  those  elements  in 
which  the  seed  is  poorest,  viz.,  calcium,  sodium  and 
chlorine.  It  follows,  therefore,  that  the  leaf  supple- 
ments the  inorganic  deficiencies  of  the  seed.  The 
leaf,  in  most  cases,  contains  much  more  of  the  dietary 
essential,  fat-soluble  A,  than  is  found  in  any  seed, 
so  that  combinations  of  leaf  and  seed  prove  more 
satisfactoiy  for  the  nutrition  of  an  animal  than  do 
mixtures  of  seeds  alone.  The  leaf  contains  protein 
and  amino-acids  which  result  from  digestion  of  pro- 
teins as  does  the  seed.  The  amount  varies  from  8 
per  cent  of  protein  (nitrogen  X  6.25)  in  such  fleshy 
leaves  as  the  cabbage,  after  drying,  to  more  than 
15  per  cent  m  the  dr>^  alfalfa  or  clover  leaf.  The 
seeds  vsiry  in  their  content  of  protein  from  about  10 
to  25  per  cent.  The  leaf  proteins  appear,  from 
the  data  available,  to  supplement  and  enhance  in 
some  degree  the  value  of  the  seed  proteins  ^vith  which 
fchey  are  combined.  The  leaf  supplements,  therefore, 
all  the  nutritive  deficiencies  of  the  seed,  but  not 
necessarily  in  a  highly  satisfactory  manner. 

It  is  interesting  to  reflect  upon  the  reasons  why 
the  leaf  of  the  plant  should  show  such  decided  dif- 
ferences in  its  nutritive  properties  as  contrasted 
with  the  seed.    A  consideration  of  the  difference  in 


44      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

function  of  the  two  gives  the  clue  to  the  cause.  The 
seed  consists  of  a  germ,  which  forms  in  most  cases 
but  a  very  small  part  of  the  entire  seed,  together 
with  a  relatively  large  endosperm.  The  germ  con- 
sists of  living  cells,  which  respire  and  are  capable  of 
multiphcation  (germination)  when  the  conditions 
are  favorable.  In  the  wheat  kernel  the  germ  con- 
stitutes about  5  per  cent  of  the  entire  seed.  The 
endosperm,  on  the  other  hand,  consists  largely  of 
reserve  food  materials  such  as  protein,  starch, 
sugars,  fats  and  mineral  salts.  It  is  not  living  matter, 
and  contains  few  cellular  elements.  The  endosperm 
is,  therefore,  in  most  respects  comparable  to  a  mix- 
ture of  purified  food-stuffs.  There  is,  as  experiments 
have  abundantly  demonstrated,  relatively  little  of 
the  dietary  factor,  water-soluble  B,  in  the  endosperm, 
and  relatively  much  in  the  germ  or  embryo.  The 
same  is  true  for  the  second  unidentified  dietary 
factor  fat-soluble  A.  This  is  practically  absent  from 
the  endosperm,  but  is  fairly  abundant  in  the  germ. 
Since  the  latter  represents  so  small  a  portion  of  the 
entire  seed,  the  seed  itself  is  too  poor  in  this  sub- 
stance, in  nearly  all  cases,  to  supply  the  needs  of  a 
growing  animal. 

The  leaf  of  the  plant,  on  the  other  hand,  is  very 
rich  in  cells,  and  in  most  cases  contains  but  Uttle  re- 
serve food  material.  It  is  the  laboratoiy  of  the  plant. 
Chlorophyll,  its  green  pigment,  enables  it  to  make 
use  of  the  energy  of  the  sunhght,  and  from  the 
carbonic  acid  gas  which  it  absorbs  from  the  air, 


DIETARY  PROPERTIES  OF  \^GETABLES       45 

together  with  water  and  mineral  salts,  which  it 
absorbs  from  the  soil  thi'ough  its  roots,  it  builds 
up  proteins,  starch,  sugars  and  fats,  which  are  used 
for  the  growth  of  new  plant  tissue,  or  for  storage  in 
the  seed,  tuber  or  other  storage  organs.  The  sur- 
faces of  the  leaf  are  a  mosaic  of  living  cells.  They 
contain  all  the  chemical  complexes  which  are  nec- 
essaiy  for  the  nutrition  of  the  animal  cells,  and  are 
qualitatively    complete   foods. 

The  quality  of  the  leaf  from  the  dietary  standpoint 
may  vary  to  a  considerable  extent.  Some  lea\xs  are 
thin  cellular  structures,  which  diy  easily  in  the  sun 
when  separated  from  the  plant.  In  others,  as  the 
cabbage,  the  leaf  is  in  some  degree  modified  as  a 
storage  organ,  and  contains  a  considerable  amount 
of  sugars.  The  cabbage  leaf  likewise  contains  more 
than  the  ordinary  amount  of  cellulose,  which  is  its 
skeletal  tissue.  Its  dietary  properties  are  modified 
by  these  pecuharities  in  that  the  cellular  elements 
are  diluted  by  the  more  inert  tissues  and  reserv^e 
food  substances  in  the  leaf.  The  freer  a  leaf  is  from 
the  function  of  a  storage  tissue,  the  more  intensified 
wiU  be  its  leaf  properties  as  a  food.  The  fleshy  leaves 
tend  to  have  in  some  degree  the  dietaiy  properties 
of  the  seed,  and  stand  intermediate  between  the 
leaves,  which  ax-e  thin,  and  dry  easily,  and  the  seed 
in  this  respect. 

The  Tubers. — After  the  seeds,  the  tubers  of  cei^ 
tain  plants  constitute  one  of  the  most  important 
classes  of  energy-yielding  foods.     The  potato  and 


46      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

sweet  potato  are  by  far  the  most  important  rep- 
resentatives of  this  group  in  Europe  and  the  Amer- 
icas, but  several  other  kinds  of  tubers  are  widely 
used  as  human  food  in  the  Orient.  An  examination 
of  the  potato  has  been  recently  made,  which  reveals 
the  special  dietary  properties  of  this  tuber  to  be  just 
what  we  should  expect  from  its  function  as  a  storage 
organ  for  reserve  food  in  the  plant.  The  functions 
of  the  potato  are  twofold,  viz.,  to  reproduce  the 
plant  in  the  following  generation,  and  to  furnish 
a  food  supply  for  the  young  potato  plantlet  while 
it  is  developing  root  and  leaf  systems  which  make 
it  independent  of  the  food  stored  in  the  old  tuber. 
The  '^eyes"  of  the  potato  represent  groups  of  cells 
which  are  analogous  to  the  germ  of  the  seed.  These 
are  the  points  at  which  the  potato  sprouts  when  the 
conditions  are  appropriate.  There  is  underneath 
the  skin  of  the  potato  a  layer  of  cells  which  are  alive 
and  respiring  during  the  life  of  the  tuber,  but  the 
interior  of  the  potato  consists  almost  entirely  of 
water,  starch,  protein,  and  to  some  extent  of  mineral 
salts.  The  cellular  structures  in  the  interior  are 
gorged  with  starch,  etc.,  and  this  portion  is  therefore 
analogous  in  its  dietary  properties  with  the  endo- 
sperm of  the  seed.  Both  are  comparable  to  a  mixture 
of  purified  protein,  carbohydrate,  and  salts,  which, 
as  we  have  previously  seen,  is  not  capable  of  support- 
ing hfe.  This  portion,  hke  the  portion  of  the  rice 
kernel,  which  remains  after  polishing,  is  almost 
lacking  in  both  the  chemically  unidentified  dietary 


DIETARY  PROPERTIES  OF  VEGETABLES       47 

essentials,  fat-soluble  A  and  water-soluble  B,  and 
accordingly  cannot  support  life  even  though  it  may 
have  an  appropriate  chemical  composition  as  shown 
by  analysis.  The  potato  is  to  be  classed  wdth  the 
seeds  in  its  dietary  properties,  because  it  consists 
largely  of  reserve  food  materials  and  relatively  little 
of  cellular  elements.  The  results  available  indicate 
that  if  the  potato  is  steamed  and  the  thin  paperlike 
skin  removed  without  the  loss  of  the  cellular  layer 
which  hes  just  underneath,  it  wdll  contain  relatively 
more  of  the  fat-soluble  A,  a  lack  of  which  leads  to 
the  development  of  the  pecuUar  eye  conditions  pre- 
viously described,  than  do  the  cereal  grains.  Al- 
though it  has  not  been  subjected  to  experimental 
test,  it  would  seem  that  a  potato  which  is  pared  in 
the  ordinary  way  and  the  paring  discarded,  is 
changed  in  its  dietary  properties  in  much  the  same 
way  as  is  the  rice  kernel  during  the  polishing  process. 
In  the  latter,  the  germ  and  the  bran  layer  are  both 
rubbed  off,  lea\ing  the  endosperm  without  the  small 
quota  of  cellular  elements  wliich  it  possessed  in  its 
natural  state,  and  is  correspondingly^  changed  in  its 
food  value  (see  legend  to  Chart  3).  The  protein  of 
the  potato  is  not  quite  so  valuable  for  growth  as  that 
of  the  cereal  grains  w^hen  fed  as  the  sole  source  of 
this  dietary  factor.^ 

There  have  been  a  number  of  experiments  of  short 
duration  which  gave  results  which  indicate  that  in 
the  human  subject  the  nitrogen  of  the  potato  is  of 
extraordinary  value  for  replacing  that  lost  tln^ough 


48     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

daily  metabolism  in  the  adult.  McCoUum,  Sim- 
monds  and  Parsons,  have  tested  this  question  by 
comparing  with  the  protein  of  the  cereal  grains  the 
value  of  the  nitrogen  of  the  potato  when  this  tuber 
was  supplemented  in  such  a  manner  as  to  make 
good  all  of  its  deficiencies  except  protein.  The 
experiments  involved  growth  tests  in  the  young  rat. 
The  results  show  conclusively  that  potato  nitrogen 
falls  considerably  below  the  value  for  growth  pos- 
sessed by  the  indi\ddual  cereal  gi-ains,  when  each  of 
these  serves  as  the  sole  supply  of  the  digestion  prod- 
ucts of  protein. 

The  Roots  Employed  as  Food.  —  The  same  rea- 
soning applies  to  the  root  crops  as  to  the  potato, 
with  respect  to  the  relation  between  dietary  prop- 
erties and  biological  function.  The  roots  which  we 
employ  as  food  are  those  which  are  liighly  modified 
as  storage  organs,  and  resemble  the  potato  in  con- 
taining a  ver}^  high  water  and  starch  content,  and 
but  very  httle  protein.  Like  the  potato,  there  is  a  cel- 
lular layer  at  the  periphery,  and  the  interior  is  loaded 
with  reserve  food-stuffs.  Appropriate  feeding  tests 
have  shown  that  the  properties  of  the  beet  resemble 
-those  of  the  seed  and  the  tuber,  rather  than  those  of 
the  leaf.^  The  fleshy  roots  and  the  potato  and  the 
sweet  potato  have  an  inorganic  content  which  re- 
sembles that  of  the  seed  in  a  general  way,  so  that  an 
inspection  of  the  anatytical  data  relating  to  the 
composition  of  the  ash  of  the  seeds,  tubers  and  roots, 
gave  no  promise  that  the  combination  in  diets  of 


DIETARY  PROPERTIES  OF  VEGETABLES        49 

seeds  with  either  of  the  latter  classes  of  food-staffs 
would  correct  the  inorganic  deficiencies  of  the  fonner. 
Feeduig  experiments  in  which  a  seed  and  a  tuber 
were  combuied,  and  so  supplemented  wdth  purified 
protein,  and  fat-soluble  A  (in  butter-fat),  that  all 
the  deficiencies  of  the  mixture,  except  the  inorganic, 
were  made  good,  have  shown  that  in  the  combinations 
of  each  of  the  more  important  seeds  with  the  potato, 
the  resulting  mineral  supply,  which  is  derived  solely 
from  the  natural  foods  themselves,  is  not  of  a  char- 
acter suitable  for  the  support  of  growth.^  The  con- 
tent of  the  elements,  calcium,  sodium  and  chlorme 
must  be  augimiented  by  greater  amounts  before  such 
food  mixtures  are  complete  with  respect  to  their 
mineral  content.  Xo  studies  have  as  yet  been  made 
to  determine  the  biological  value  of  the  nitrogen  of 
the  tubers  other  than  the  potato,  and  none  at  all  of 
the  edible  roots. 

From  the  results  of  systematic  feeding  trials  wdth 
mixtures  of  seeds  alone  and  the  same  with  single  and 
multiple  purified  food  additions,  and  the  same  t>^e 
of  expermient  using  certain  of  the  tubers  and  root 
foods  in  place  of  the  seeds,  it  is  shoTNTi  that  all  these 
classes  of  foodstuffs  resemble  one  another  in  all  re- 
spects except  in  the  high  content  of  water  m  the 
tubers  and  roots.  In  the  diy  state  they  are  all  much 
like  the  seeds,  but  there  is  one  minor  difference  which 
should  be  mentioned.  The  most  miportant  difference 
lies  in  the  character  of  the  nitrogenous  compounds. 
In  the  seeds  the  nitrogen  is  almost  all  contained  in 


50     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

the  form  of  true  protein.  In  the  tubers  and  edible 
roots  most  of  it  is  in  the  foim  of  much  simpler  com- 
pounds, a  part  being  the  same  amino-acids  which  are 
derived  from  proteins  on  digestion. 

It  is  possible  to  prepare  diets  derived  solely  from 
vegetable  products  which  will  nourish  an  animal 
during  growth  and  throughout  life  in  a  very  satis- 
factory manner,  but  it  is  a  surprisingly  difficult  task 
to  prepare  for  the  omnivera,  an  adequate  diet  com- 
posed entirely  of  food-stuffs  of  plant  origin.  AATiile 
many  of  the  seeds  contain  nothing  of  a  detrimental 
character,  many  of  the  leaves,  when  eaten,  undoubt- 
edly do  introduce  into  the  body  substances  which 
have  more  or  less  injurious  effects.  The  nature  of 
these  cannot  be  stated  at  the  present  time,  but  the 
possibility  that  there  m.ay  be  an  injurious  effect 
brought  about  by  prolonged  administration  of  such 
bodies  as  the  tannins,  the  glucosides  and  oxalic  acid, 
certain  organic  bases  which  in  some  cases  resemble 
certain  of  the  alkaloids,  and  in  some  leaves  the  pres- 
ence of  alkaloids  which  are  highly  active  pharmaco- 
logically, can  easily  account  for  the  fact  that  with 
all  rations  of  strictly  vegetable  origin  one  would 
not  have  optimum  nutrition.  McCollum  and  Sim- 
mon ds  have  in  a  long  Ust  of  trials  with  mixtures  of 
leaves  and  seeds  been  unable  to  secure  the  opti- 
mmn  of  well-being  in  omnivorous  animals.  It  is 
worthy  of  the  greatest  emphasis  that  in  our  hundreds  of 
trials  with  diets  derived  entirely  from  vegetable  sources, 
we  have  not  succeeded  in  producing  optimum  results  in 


DIETARY  PROPERTIES  OF  XTGETABLES   51 

the  nutrition  of  an  omnivorous  animal  the  rat.  Certain 
of  the  animals  which  we  have  restricted  to  foods  of 
plant  origin,  have  done  so  well  that  we  should  in  the 
absence  of  much  experience  with  diets  of  excellent 
quality,  have  considered  them  to  be  normal  in  every 
respect.  It  should  be  emphasized  that  the  average 
performance  of  a  group  of  people  or  animals  li\'ing 
upon  a  varied  diet  cannot  safely  be  assumed  to  repre- 
sent the  best  of  which  they  are  capable.  In  the 
study  of  diets  the  author  and  his  colleagues  have 
kept  constantly  in  mind  the  best  results  we  have  ever 
seen  in  the  nutrition  of  animals,  as  exemplified  in 
rapidity  of  growth,  ultimate  size  attained,  number  of 
young  produced,  and  the  success  with  which  these 
were  reared,  and  have  attempted  to  assign  to  ever^^ 
experimental  groujD  its  legitimate  place  on  a  scale  of 
performance,  which  has  complete  failure  to  either 
grow  or  long  remain  ahve  as  the  one  extreme,  and 
the  optimum  of  which  the  animal  is  capable  as  the 
other. 

In  connection  with  the  statement  which  has  just 
been  made  regarding  the  strict  vegetarian  diet,  that 
it  does  not,  so  far  as  has  been  observed,  induce  the 
best  results  in  the  nutrition  of  the  omnivora,  it  should 
be  added  that  in  human  dietary  practice  what  is 
generally  designated  as  vegetarianism  is  in  reality 
something  veiy  different.  Alany  people  hold  that 
they  are  adhering  to  vegetarian  dietary  habits,  who 
in  reality,  take  in  addition  to  foods  of  plant  origin, 
milk  or  eggs  or  both.    This  type  of  diet  will  give  very 


52      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

much  better  results  than  can  be  secured  from  the 
use  of  vegetable  foods  alone.  Lacto-vegetarianism 
should  not  be  confuesd  with  strict  vegetarianism. 
The  former  is,  when  the  diet  is  properly  planned, 
the  most  highly  satisfactory  plan  which  can  be 
adopted  in  the  nutrition  of  man.  The  latter,  if 
strictly  adhered  to,  is  fraught  with  grave  danger 
unless  the  diet  is  planned  by  one  who  has  extensive 
and  exact  knowledge  of  the  special  properties  of  the 
various  food-stuffs  employed. 


CHAPTER  III 

THE    VEGETARI-IN    DIET 

It  has  been  pointed  out  in  the  preceding  chapters 
that  it  is  not  possible  to  make  a  diet  derived  entkely 
from  seeds  or  seed  products,  which  ^ill  adequately 
nourish  an  animal  during  growth,  and  it  may  be 
added  that  such  diets  will  not  even  maintain  a  fully 
gi'own  anmial  in  a  state  of  health  and  normal  physi- 
ological activity  over  a  long  period.  Without  an 
appropriate  supplementing  of  seed  mixtures  with 
the  elements,  calcium,  sodium  and  chlorme,  no  ap- 
preciable amount  of  growth  has  been  secured  with 
seed  mixtures,  in  our  extensive  experience.  It  was 
further  pointed  out  that  the  leaf  is  a  very  different 
thing  from  the  seed,  tuber  or  root,  from  the  dietary 
standpoint,  and  these  differences  in  nutritive  prop- 
erties can  be  correlated  with  differences  in  function. 
The  seed  is  a  storage  organ  of  the  plant,  and  is  filled 
with  a  reserve  supply  of  proteins,  carbohydrates,  fats 
and  mineral  salts.  It  is  in  great  measure  non-h^ang 
matter,  and  indeed  much  of  the  contents  of  the  seed 
was  never  a  part  of  living  matter,  but  only  the  prod- 
uct of  it.  In  the  leaf  of  the  plant  we  have  a  tissue 
which,  during  life,  was  very  active  in  the  manifesta- 
tions of  the  properties  of  lining  matter.    With  these 

53 


54      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

differences  in  function,  it  was  pointed  out,  there  are 
found  corresponding  diffei^ences  in  the  dietary  values 
of  the  two  types  of  foods,  the  latter  being  much  more 
nearly  complete  foods  chemically,  than  are  the  seeds, 
tubers  and  roots. 

Let  us  consider  briefly  the  bearing  of  these  obser- 
vations on  the  w^hole  subject  of  human  and  animal 
nutrition.  It  has  been  pointed  out  that  for  many 
years  the  protein  and  energy  value  and  its  digest- 
ibility were  assumed  to  determine  the  value  of  a 
food.  The  chemist  is  able  to  determine  approxi- 
mately the  amount  of  protein  or  rather  its  content 
of  nitrogen  which  is  ta,ken  as  a  measure  of  the  amount 
of  protein  and  the  fuel  value  of  a  food,  and  by  means 
of  experiments  on  animals,  the  extent  to  which  a 
given  food  is  digested  and  absorbed.  He  can  even 
tell  by  a  study  of  the  relation  between  the  amounts 
of  oxygen  absorbed  by  the  tissues,  and  the  amount 
of  carbon  dioxide  given  off  whether  the  animal  is 
burning  sugar  or  fat  in  order  to  obtain  its  energy. 
The  nitrogen  eliminated  in  the  urine  serves  as  a  meas- 
ure of  the  destruction  of  protein  in  the  body.  With- 
out in  the  least  attempting  disparagement  of  the 
value  of  the  services  of  the  chemist  in  the  study  of 
the  problems  of  nutrition,  it  may  truthfully  be 
said  that  both  his  ordinary  and  his  unusual  and 
most  searching  methods  for  the  analysis  of  food- 
stuffs fail  to  throw  any  great  amount  of  hght  on 
the  value  of  a  food  or  mixture  of  foods  for  induc- 
ing growth. 


THE  \^GETARIAN   DIET  55 

Id  addition  to  the  cereal  grains,  wheat,  oat,  maize, 
rye,  barley  and  rice,  the  products  of  the  vegetable 
garden  wliich  supphed  leafy  vegetables,  cabbage, 
lettuce,  spinach,  cauliflower,  brussels  sprouts,  chard, 
celery,  various  '^ greens,'^  etc.;  roots,  such  as  the 
radish,  turnip  and  beet;  tubers,  such  as  the  potato 
and  sweet  potato,  we  have  had  available  as  food  an 
abundance  of  meats  and  of  dairy  products.  It  is 
not  strange  that  ^^'itll  such  a  supply  of  foods  it  should 
have  been  taken  for  granted  that  any  diet  consisthig 
of  wholesome  foods,  combined  in  such  proportions 
and  taken  in  such  quantities  as  would  fmnish 
the  amounts  of  protein  and  energy  wliich  exper- 
iments on  man  and  animals  had  sho\\Ti  to  be  neces- 
sary under  specified  conditions  of  hving,  whether  at 
rest  or  at  work,  should  prove  satisfactory  for  the 
maintenance  of  health  ua  the  adult  and  of  normal 
gro^^i:h  in  the  young.  An  appreciation  of  the  funda- 
mental importance  of  employing  proper  combinations 
of  foods,  VN'as  impossible,  until  the  systematic  efforts 
described  ua  the  first  two  chapters,  were  made  to 
simplify  the  diet  as  far  as  possible,  and  to  derive  it 
from  restricted  sources.  These  studies  have,  when 
the  results  were  apphed  to  the  haterpretation  of  the 
quahty  of  the  diets  of  man  in  several  parts  of  the 
world,  revealed  the  fact  that  man  is  frequently 
faihng  to  make  the  wisest  selection  of  food.  Health 
and  efficiency  can  be  greatly  improved  by  appMng 
the  knowledge  which  we  now  possess  concerning 
the  special  properties  of  several  classes  of  foods,  to 


56     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

the  selection  of  the  articles  which  shall  make  up  the 
daily  diet. 

The  biological  method  for  the  analysis  of  single 
food-stuffs  and  mixtures  of  food-stuffs  has  made  it 
evident  that  the  older  practice  of  regarding  protein, 
energy  and  digestibility  as  the  criteria  of  the  value  of 
a  food  mixture,  must  be  replaced  by  a  new  method  of 
presentation  of  the  subject  based  upon  a  biological 
classification  of  the  food-stuffs,  the  latter  having  its 
foundation  in  the  function  of  the  substance  employed 
in  the  diet.  Such  a  method  of  presentation  of  the 
subject  of  food  values  offers  convincing  evidence  of 
the  necessity,  for  the  proper  selection  of  food,  that 
dietary  reforms  are  greatly  needed  in  many  parts  of 
the  world. 

There  has  been  much  discussion  of  the  relative 
merits  of  the  vegetarian  diet  for  man  as  compared 
with  diets  largely  derived  from  vegetable  foods  but 
more  or  less  liberally  supplemented  with  foods  of 
animal  origin.  This  question  has  been  discussed 
principally  from  the  point  of  view  of  the  supposed 
detrimental  effects  of  a  diet  containing  a  high  protein 
content,  and  the  supposed  beneficial  effects  of  a 
sparing  consmnption  of  protein,  and  from  the  point 
of  view  that  there  are  sound  ethical  reasons  why 
man  should  abstain  from  the  use  of  animal  foods. 
The  adherents  of  the  latter  extreme  view  have  never 
become  numerous,  partly  because  the  average  in- 
dividual has  not  the  self-control  to  enable  him  to 
forego  the  use  of  meats,  milk  and  eggs,  on  account 


THE  VEGETARIAN  DIET  57 

of  their  appetizing  qualities,  and  partly  because  the 
chances  of  one's  succeeding  in  the  selection  of  a 
strictly  vegetarian  diet  which  would  maintain  such 
a  state  of  physiological  well-being  as  would  make 
possible  the  continuation  of  his  hne  are  very  small. 
Concernmg  the  ethical  considerations  involved  in 
the  eating  of  animal  foods,  nothing  need  be  said  here. 
The  relative  merits  of  the  vegetarian  as  compared 
^dth  the  mixed  diet,  and  the  evidence  regarding  the 
desirability  of  taking  a  low  or  high  protein  intake, 
may  next  receive  our  attention. 

The  most  elaborate  attempt  to  test  the  relative 
merits  of  the  strictly  vegetarian  diet  as  contrasted 
with  the  omnivorous  type,  was  made  by  Slonaker.^ 
He  fed  a  group  of  young  rats  on  a  hst  of  23  vegetable 
foods,  allowing  them  free  choice  within  limits.  For 
comparison,  a  similar  group  were  fed  the  same  foods 
of  vegetable  origin,  but  in  addition  animal  food  was 
given  in  moderate  quantities.  Since  several  natural 
foods,  raw  or  prepared,  were  offered  at  a  time,  and 
the  anim^als  were  allowed  free  choice  as  to  what  they 
should  eat,  and  since  no  effort  was  made  to  keep 
track  of  the  food  consumption,  or  the  relative 
amounts  of  the  different  foods  eaten,  the  results 
cannot  be  employed  for  critical  examination  except 
in  a  limited  way.  The  results  are  of  the  greatest 
interest  in  shomng  how  far  instinct  fails  to  guide 
an  animal  in  the  selection  of  its  food.  .  Slonaker's 
hst  of  foods  included  nearly  everything  which  a 
vegetarian  in  southern  California  would  be  hkely 


58     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

to  have  on  his  table  during  the  year,  and  included 
seeds,  the  milhng  products  of  seeds  and  leafy  veg- 
etables, tubers  and  roots. 

The  vegetarian  group  grew  fairly  well  for  a  time, 
but  became  stunted  when  they  reached  a  weight  of 
about  60  per  cent  of  the  normal  adult  size.  They 
never  increased  in  size  beyond  this  point.  The 
omnivorous  controls  grew  steadily  to  what  may  be 
regarded  as  the  normal  size  for  the  adult.  The 
vegetarians  lived,  on  an  average  for  the  entire  group, 
555  days,  whereas  the  omnivora  had  an  average  span 
of  life  of  1020  days.  The  vegetarian  rats  grew  to  be 
approximately  half  as  large,  and  hved  half  as  long 
as  did  their  fellows  which  received  animal  food. 
Slonaker  drew  the  conclusion  that  a  strictly  veg- 
etarian diet  is  not  suitable  for  the  nourishment  of  an 
omnivorous  anim-al,  but  was  unable  to  say  why  this 
should  be  true. 

The  results  of  Slonaker  were  published  in  1912, 
and  just  at  the  timx  when  McCollum  and  Davis  were 
securing  the  experimental  data  which  revealed  the 
differences  in  the  growth-promoting  power  of  fats 
from  different  sources  and  which  estabhshed  the 
fact  that  a  hitherto  unsuspected  dietary  essential 
existed.  They  fed  their  diet  of  relatively  pure  food- 
stuffs described  on  page  16  with  various  fats  of  both 
anim^al  and  vegetable  origin  and  found  that  no  fat 
which  was  derived  from  plant  tissues  came  in  the 
growth-prom^oting  class  along  with  butter  fat,  the 
fats  of  egg  yolk,  and  of  the  glandular  organs.     It 


THE  VEGETARIAN  DIET  59 

seemed  to  McCollum  and  Davis  that  the  most 
probable  explanation  of  the  results  of  Slonaker  was 
the  absence  or  shortage  in  his  vegetarian  diet  of  the 
dietary  essential  which  is  furnished  so  abundantly 
by  butter  fat,  and  which  later  came  to  be  designated 
as  fat-soluble  A  and  to  a  low  protein  intake.  With 
this  idea  in  mind  the^'  tried  during  the  summer  of 
1914  an  experhnent  similar  to  that  of  Slonaker 's,  but 
modified  so  as  to  give  the  animals  a  much  higher 
protem  content  than  his  z^ats  probabl}^  took.  It 
seemed  that  if  Slonaker's  vegetarian  rats  ate  hberally 
of  such  leaves  as  cabbage  and  other  leafy  vegetables, 
the  protein  content  of  which  in  the  fresh  condition 
does  not  as  a  rule  exceed  2  per  cent,  the  content  of 
other  constituents  of  the  diet  in  protein  might  not 
be  high  enough  to  give  the  entii^  mixture  consumed, 
a  protein  content  sufficiently  liigh  to  promote  growth 
at  the  optimum  rate. 

^IcCollum  and  Da\ds,  therefore,  fed  their  rats  a 
diet  which  afforded  them  a  choice  among  the  follow- 
ing list  of  foods:  wheat,  maize,  lye  and  oat  kernels, 
cooked  diy  na^y  beans,  peas,  wheat  germ,  corn 
gluten,  wheat  gluten,  flax-seed  oil  m.eal,  green  clover, 
green  alfalfa  leaves,  onions  and  peanuts.  It  vnW  be 
observed  that  in  this  Ust  there  are  seveial  vegetable 
foods  ha\ing  unusually  liigh  protein  contents.  Corn 
gluten,  which  is  a  product  of  the  com  starch  manufac- 
ture, contains  about  25  per  cent  of  protein;  wheat 
gluten,  prepared  by  washing  gi'ound  wheat  free  from 
starch,  contains  about  86  per  cent;  flax-seed  oil  meal, 


60     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

as  much  as  30  per  cent,  and  wheat  germ  about  30  per 
cent  of  protein.  Since  animals  are  knowTi  to  grow 
well  on  many  diets  containing  15  to  18  per  cent 
of  protein,  it  seemed  that  with  these  things  to 
select  from,  one  possible  cause  of  failure  in  Slonaker's 
experiments,  viz.,  too  low  a  protein  intake,  would  be 
avoided.  McCollum  and  Davis  had  not  at  that  time 
discovered  in  the  leaf  the  source  of  the  dietaiy  essen- 
tial, fat-soluble  A,  although  it  is  now  known  that  the 
leafy  foods  enable  the  herbivorous  animal  to  thrive 
on  his  diet  derived  entirely  from  plant  tissues.  It  was 
then  assumed  that  when  both  the  leaves  and  so 
many  different  seeds  as  well  as  the  germ  was  supplied 
there  could  be  little  doubt  that  everything  which  a 
herbivorous  animal  requires  was  present  in  the  foods 
supplied. 

The  rats  fed  this  wide  variety  of  vegetable  foods, 
and  with  a  most  liberal  supply  of  protein,  duplicated 
in  all  respects  the  results  which  Slonaker  had  de- 
scribed. They  grew  at  about  half  the  normal  rate 
for  the  first  few  weeks,  then  became  permanently 
stunted,  none  ever  reaching  a  size  much  greater  than 
half  that  of  the  average  normal  adult.  The  addition 
of  butter  fat  to  the  diet  of  some  of  these  animals 
failed  to  benefit  them  in  any  noticeable  degree.  The 
answer  to  the  question  as  to  why  rats  do  not  thrive 
on  such  strictly  vegetarian  food  mixtures  was  not 
secured  from  these  experiments.  It  was,  however, 
soon  after  learned  wherein  lay  the  cause  of  failure  of 
animals  so  fed. 


THE  VEGETARIAN   DIET  61 

McCollum,  Simmonds  and  Pitz,  began  in  1915  a 
series  of  feeding  experiments  in  which  the  diets  of 
rats  were  derived  solely  from  a  mixture  of  one  seed 
and  one  diy  leaf.-  In  marked  contrast  to  the  failure 
of  animals  to  grow  on  any  mixtures  of  seeds  it  was 
found  that  in  many  cases  a  mixture  of  a  seed  with  a 
leaf  formed  a  diet  on  which  considerable  growth 
could  be  secured.  Even  polished  rice,  which  as  has 
been  already  described,  requires  four  types  of 
supplementing,  \dz,  protein,  mineral  salts,  fat- 
soluble  A  and  water-soluble  B,  before  it  becomes 
dietetically  complete,  was  found  to  induce  fairly 
good  growth  when  fed  with  ground  alfalfa  leaves  in 
the  proportion  of  60  per  cent  of  the  former  to  40  per 
cent  of  the  latter.  On  this  simple  monotonous  mix- 
ture, young  rats  grew  from  w^eaning  time  to  83  per 
cent  of  the  normal  adult  «"ze,  and  one  female  even 
produced  two  Utters  of  young,  both  of  ^vhich  w^ere, 
however,  allowed  to  die  within  a  few^  days.  A  mix- 
ture of  rolled  oats,  60  per  cent,  and  alfalfa  leaves, 
40  per  cent,  ground  together  makes  a  Yery  much 
better  diet.  On  this  simple  mixture  young  rats  have 
been  observed  to  grow  to  the  normal  adult  size,  and 
to  reproduce  and  rear  young.  One  female  reared 
fourteen  out  of  seventeen  young  born  in  three  litters. 
INIaize  and  alfalfa  leaf,  wheat  and  alfalfa  leaf,  are 
not  so  satisfactory^  for  the  production  of  growth  as 
is  a  mixture  of  rolled  oats  and  alfalfa  leaves.  INIix- 
tures  of  the  latter  leaf  with  legume  seeds,  peas  and 
beans,  give  still  poorer  results.     (Chart  6.)     These 


62     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

results  made  it  evident  that  there  is  nothing  in 
vegetarianism  per  se,  which  makes  it  impossible  to 
nourish  an  omnivorous  animal  in  a  satisfactory 
manner.  It  is  only  necessary  to  make  a  proper  selec- 
tion of  food-stuffs,  and  to  combine  them  in  the  right 
proportions.  In  all  the  experiments  described,  in 
which  the  diet  was  made  up  of  so  simple  a  mixture 
as  one  leaf  and  one  seed,  they  had  not  obtained 
the  optimum  of  growth,  reproduction  or  rearing  of 
young. 

It  seemed  probable  that  the  reason  why  they  did 
not  more  closely  approximate  the  optimum  in  the 
nutrition  of  animals  restricted  to  a  cereal  grain  and 
a  leaf,  might  He  in  too  low  a  protein  mixture,  or  a 
protein  mixture  which  was  not  of  very  high  bio- 
logical value.  In  1915,  McCollum,  Simmonds  and 
Pitz  ^  fed  a  group  of  young  rats  on  a  monotonous 
mixture  consisting  of  maize  50  per  cent,  alfalfa 
leaf  (dry)  30  per  cent,  and  cooked  (dried)  peas,  sub- 
sequently dried,  20  per  cent.  The  three  ingT-edients 
were  ground  together  so  finely  that  they  could  not 
be  picked  out  and  eaten  separately.  This  diet  in- 
duced growl  h  at  approximately  the  normal  rate  and 
the  production  and  rearing  of  a  considerable  number 
of  young.  The  young  grew  up  to  the  fuU  adult  size 
and  were  successful  in  the  rearing  of  their  offspring. 
Without  ever  tasting  anything  other  than  this  mo- 
notonous food  mixture,  as  their  sole  source  of  nutri- 
ment after  the  weaning  peiuod,  this  family  of  rats 
remained  nearly  normal,  and  successfully  weaned  the 


THE  VEGETARIAN   DIET  63 

young  of  the  fourth  generation,  with  no  apparent 
diminution  in  vitahty.  At  this  point  the  experiment 
was  discontinued. 

The  failure  of  Slonaker's  rats  to  thrive  on  the 
vegetarian  diet  is  to  be  explained  on  the  basis  of 
several  faults.  In  the  first  place,  the  diet  was  of 
such  a  nature  that  the  animals  could  hardly  do  other- 
wise than  take  a  rather  low  protein  intake.  Sec- 
ondly, the  leaves,  which  foimed  the  only  constituents 
of  the  food  supply  which  contained  enough  mineral 
elements  to  support  growth,  were  fed  in  the  fresh 
condition.  In  tliis  form  the  water  content  and  bulk 
is  so  great  that  it  would  be  practically  impossible 
for  an  animal  whose  digestive  apparatus  is  no  more 
capacious  tlian  that  of  an  omnivora,  to  eat  a  sufficient 
amount  of  leaf  to  correct  the  inorganic  deficiencies 
of  the  rest  of  the  mixture,  which  consisted  of  grains, 
seeds,  tubers,  and  root  foods.  The  same  physical 
limitations  would  hkewise  determine  that  the  animals 
would  fail  to  secure  enough  of  the  fat-soluble  A  to 
supplement  the  deficiency  of  all  the  ingredients  of 
their  diet  other  than  the  leaves  in  respect  to  this 
factor.  This  would  not  form  so  important  a  fault 
as  the  inorganic  deficiencies,  but  would  be  an  im- 
portant depressing  factor.  Thirdly,  success  or 
failure  would  turn  in  great  measure  on  the  extent 
to  which  the  animals  would  be  guided  by  instinct  in 
the  selection  of  the  proportions  of  the  several  types 
of  food-stuffs  which  was  offered  them.  In  the  opin- 
ion of  the  author  the  appetite  is  by  no  means  so 


64     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

safe  a  guide  for  the  proper  selection  of  foods  as  has 
generally  been  supposed. 

From  the  results  of  the  experiments  just  de- 
scribed it  was  necessary  to  conclude  that  the  leaf 
differs  from  the  seed  in  that  it  contains  in  satis- 
factory amounts  the  dietary  factors  which  are  found 
in  the  seeds  in  too  small  amounts.  These  include  the 
three  inorganic  elements,  calcium,  sodium  and  chlo- 
rine, the  fat-soluble  A  and  a  protein  supply  which 
supplements  at  least  in  some  degree  the  proteins  of 
the  seed.  These,  it  will  be  remembered,  are  the 
three  and  only  purified  food  factors  which  need  be 
added  to  each  of  the  seeds  singly  in  order  to  make  it 
dietetically  complete.  It  is  therefore,  possible  to  de- 
vise a  diet  which  is  deiived  entirely  from  vegetable 
materials  which  will  produce  normal  growth  and 
the  optimum  physiological  well-being. 

At  the  Iowa  Experiment  Station,  Ewaid  ^  has  con- 
ducted extensive  experiments  of  a  character  which 
were  intended  to  demonstrate  that  the  appetite  and 
instincts  of  the  hog  serve  to  enable  it  to  make  such 
an  adjustment  of  the  relative  amounts  of  the  several 
food-stuffs  offered  it,  as  may  induce  better  results 
in  the  rate  of  growth  than  can  be  generally  secured 
when  the  adjustment  is  made  by  the  feeder,  and 
the  mixture  of  the  ingi^edients  of  the  ration  are  offered 
in  a  form  w^hich  admitted  of  no  choice  by  the  animal. 
The  data  secured  in  many  trials  seem  to  show  that 
there  is  some  basis  for  the  belief  that  this  element  of 
selection  by  the  animal  itself  is  worth  taking  ad- 


THE  VEGETARIAN   DIET  65 

vantage  of.  It  should  be  mentioned  that,  as  a  rule, 
m  all  these  trials  the  animals  were  given  a  choice  of 
only  three  foods,  one  of  these  being  a  cereal  grain, 
another,  a  protein-rich  food  and  a  tliird  a  plant  leaf. 
In  some  experiments  a  salt  mixtm^e  was  made  avail- 
able. The  reasons  for  the  employment  of  the  leaf 
as  a  never  failing  constituent  of  the  food  supply  of 
the  growing  pig  could  not  have  been  explained  be- 
fore the  studies  of  IMcCollum  and  his  co-workers, 
with  simplified  diets  and  with  diets  restricted  as  to 
source  to  a  single  food-stuff,  and  until  the  latter  had 
been  fed  with  single  and  multiple  food  additions  to 
ascertain  the  exact  nature  of  the  dietary  faults  of 
each.  In  connection  with  the  types  of  diets  em- 
ployed by  E\^"ard  it  should  be  mentioned  that  in 
case  the  animal  ate  fairly  liberally  of  all  the  food- 
stuffs offered  him,  a  sei^ious  mistake  would  be 
hardly  made,  since  the  proportions  of  the  several  con- 
stituents eaten  could  be  varied  to  a  considerable  de- 
gree and  giowth  still  take  place.  In  the  case  of  the 
mixture  of  maize  50  per  cent,  alfalfa  leaves  30  and 
peas  20,  described  above  (Chart  7)  it  has  been  found 
that  for  the  rat  these  are  the  best  proportions  in 
which  these  three  ingredients  can  be  mixed  for  the 
promotion  of  growth  and  reproduction.  It  has  been 
further  established  that  using  these  three  food-stuffs, 
a  moderate  amount  of  growth  may  be  secured,  but 
few,  if  any,  young  will  ever  be  produced  if  the  mix- 
ture fed  contains  more  than  50  per  cent  or  less  than 
20  per  cent  of  alfalfa  leaf.    The  importance  of  com- 


66     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

bining  the  natural  foods  in  the  right  proportions  is 
easily  seen  from  these  results.  It  is  interesting  to 
note  further,  that  shifting  the  proportions  of  maize, 
peas  and  leaf  in  this  mixture  over  a  range  of  20  per 
cent  does  not  materially  change  the  protein  content, 
or  indeed,  the  chemical  composition  of  the  food  mix- 
ture in  any  way,  to  a  degree  that  could  be  expected  to 
make  so  great  a  difference  in  the  state  of  nutrition 
of  the  animals  as  is  actually  observed. 

There  are  now  available  the  results  of  a  very  ex- 
tensive series  of  feeding  trials  in  which  the  rations 
were  made  up  of  one  seed,  one  leaf  and  one  legmne 
(pea,  bean)  in  various  proportions.  These  have 
failed  to  reveal  any  mixture  which  is  quite  the  equal 
of  the  first  ration  of  this  type  ever  employed,  viz., 
that  composed  of  maize  50,  alfalfa  leaf  30  and  peas  20 
per  cent.  It  is,  of  course,  easily  possible  that  better 
mixtures  of  vegetable  foods  may  be  found  by  further 
search,  but  these  results  show  very  definitely  that 
for  the  omnivorous  ty^e  of  animal,  whose  digestive 
tract  is  so  constituted  that  the  consumption  of  large 
volum.es  of  leafy  foods  is  not  possible,  it  is  by  no 
means  a  simple  matter,  if  indeed  possible,  to  derive 
the  diet  entirely  from  the  vegetable  foods,  and  se- 
cure the  optimum  of  well-being.  The  data  afforded 
by  the  experiments  described  form  a  demonstration 
of  the  fact  that  wide  variety  is  of  httle  value  as  a 
safeguard  to  nutrition.  Chemical  analysis,  no  matter 
how  thorough,  fails  to  throw  much  hght  upon  the 
dietar>^  value  of  a  food-stuff.    The  only  way  in  which 


THE  VEGETARIAN   DIET  67 

the  problems  of  nutrition  can  be  solved  is  through 
numerous  properly  planned  feeding  experiments, 
but  such  studies  were  not  possible  before  the  solution 
of  the  problem  of  successfully  feeding  mixtures  of 
purified  food-stuffs.  These  studies  led  to  the  formula- 
tion of  an  adequate  working  hypothesis  regarding 
what  factors  operate  to  make  an  adequate  diet,  and 
m.ade  possible  the  interpretation  of  the  cause  of 
success  or  of  failure  with  diets  of  the  complexity  em- 
ployed in  daily  life.  It  will  be  shown  later  that  the 
consumiption  of  milk  and  its  products  forms  the  great- 
est factor  for  the  protection  of  mankind,  in  correcting 
the  faults  in  his  otherwise  vegetarian  and  meat  diet. 
The  fact,  that  although  the  cereal  grains  each  con- 
tain every  inorganic  element  which  is  contained  in 
an  animal  body,  and  every  one  which  is  a  necessary 
constituent  of  the  diet,  but  in  too  small  amounts 
in  the  case  of  three  of  them,  to  enable  the  animals  to 
grow,  revealed  the  mineral  constituents  of  the  diet 
in  a  new  and  imxportant  light.  The  animal  is  sensi- 
tive to  either  the  actual  amounts  of  certain  of  the 
mineral  elements  in  the  food  mixture,  or  to  the  re- 
lationships among  them.  Sidney  Ringer  was  led 
in  1891  to  his  description  of  Ringer's  solution,  as  the 
result  of  the  observations  in  physiolog;^^  that  muscle 
behaves  more  nearly  normally  in  solutions  con- 
taining certain  salts  in  definite  proportions.  Ringer's 
solution  contains,  for  each  100  molecules  of  sodium 
chloride,  two  molecules  of  calcium  chloride  and  two 
to  one  molecules  of  potassium  chloride,  together  with 


68     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

a  trace  of  a  magnesium  salt.  Loeb,''  Howell  ^  and 
others  had  described  many  experiments  showing  the 
profound  effects  upon  the  subsequent  development 
of  the  eggs  of  vaiying  in  certain  ways  the  composition 
of  the  salt  solutions  in  which  unfertilized  eggs  of 
certain  marine  animals  were  kept.  In  this  way  the 
earliest  stages  of  development  which  are  ordinarily 
observed  only  in  the  fertilized  egg,  could  be  caused 
to  take  place  in  eggs  into  which  no  sperm  had  en- 
tered. In  the  nutrition  of  the  higher  animals,  it  had 
never  been  made  clear  how  dependent  the  organism 
is  on  the  rate  at  which  the  blood  stream  receives 
mineral  nutiient.  The  fact  that  the  cereal  grains 
are  too  low  in  three  inorganic  elements  to  admit  of 
growth,  made  it  clear  that  food  packages  just  as  they 
come  from  the  hand  of  Nature,  are  not  necessarily 
so  constituted  as  to  promote  health. 


CHAPTER  IV 

THE    FOODS   OF  ANIMAL   ORIGIN 

It  is  well  knowTi  from  common  observation  that 
milk,  when  it  serves  as  the  sole  food  of  the  infant, 
serves  to  keep  it  groT\T.ng  normally  and  in  good 
health  over  a  long  period.  There  has  occasionally 
arisen  a  discussion  as  to  whether  milk  is  a  suitable 
food  for  the  adult,  and  as  to  whether  it  is  the  ^^deal" 
food.  ]\lilk:,  hke  the  cereal  grains  and  most  other 
natural  foods,  contains  all  the  essential  food  elements, 
and  human  experience  teaches  us  that  the  proportions 
in  which  they  occur  in  this  product  are  much  more 
satisfactory  than  in  many  other  natural  foods.  An- 
nuals gi'ow  well  on  milk,  but  it  is  not  easy  to  find 
even  complex  food  mixtures  of  vegetable  foods  which 
will  support  optunum  nutrition  in  the  omnivora 
during  gi'owth. 

]Milk  is  deficient  in  iron,  as  is  shoTvn  by  chemical 
analysis.  It  has  long  been  known  that  there  is  de- 
posited in  the  spleen  of  the  new-born  animal  a  reserv^e 
supply  of  iron,  which  ordinarily  suffices  to  tide  it 
over  the  suckhng  period.  Ordinary  drinking  water 
almost  always  contains  small  amounts  of  non,  and 
tliis  doubtless  aids  in  some  degree  m  preventing  iron 
starvation  in  the  infant. 

69 


70     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

That  milk  is  a  complete  food,  capable  of  supplying 
all  the  nutrients  necessary  for  the  prolonged  main- 
tenance of  growth,  health  and  the  ability  to  produce 
and  rear  young,  was  shown  by  an  experiment  con- 
ducted by  the  author  at  the  Wisconsin  Experiment 
Station.  A  female  pig  was  removed  from  its  mother, 
which  was  still  nursing  it  at  the  weight  of  17  pounds. 
She  had  doubtless  eaten  of  the  mother's  ration  to 
some  extent  but  her  principle  food  had  been  her 
mother's  milk.  After  rem.oval  from  the  mother, 
this  pig  was  confiDed  in  a  pen  ha\dng  a  board  floor, 
and  was  fed  nothing  but  milk  during  a  period  of  17 
months.  During  the  first  few  months  only  whole 
milk  w^as  fed,  but  later  it  was  necessary  to  replace 
this  in  part  by  skim  milk.  The  animal  weighed  406 
pounds  at  the  age  of  thirteen  months.  At  this  age 
she  produced  eight  living  and  two  dead  pigs,  and 
successfully  brought  the  young  to  an  average  weight 
of  seventeen  pounds.  She  had  access  to  wood  shav- 
ings, and  ate  some  of  them.  There  can  be  no  doubt 
that  the  milk  which  she  consumed  was  enriched  to 
some  extent  with  iron  by  being  in  contact  with  cans 
having  part  of  the  surface  free  from  tin.  City  drink- 
ing water  was  also  furnished  and  this  contained 
appreciable  amounts  of  iron.  The  animal  must  have 
been  able  to  conserve  its  hmited  iron  supply  in  a 
ver>^  efficient  manner. 

Milk  is,  therefore,  capable  of  nourishing  the  pig 
during  many  months,  wdth  no  other  modification 
or  additions  than  small  amounts  of  iron.    That  it  is 


THE  FOODS  OF  ANIi\L\L  ORIGIN  71 

best  to  select  milk  as  a  monotonous  and  restricted 
diet  during  adult  life,  no  one  familiar  with  the  prin- 
ciples of  nutrition  would  maintain.  Milk  is,  however, 
without  doubt  our  most  important  food-stuff.  This 
is  true,  because  the  composition  of  milk  is  such  that 
when  used  in  combination  with  other  food-stuffs  of 
either  animal  or  vegetable  origin,  it  corrects  their  dietary 
deficiencies.  Combinations  of  equal  weights  of  milk 
and  one  of  the  cereal  gi^ains  give  excellent  results 
m  the  nutrition  of  animals  during  gi^owth,  and  grain 
mixtures  supplemented  \\dth  milk  support  well  in 
adult  life  the  function  of  reproduction  and  rearing 
of  3^oung.  This  is  because  of  the  excellent  quality 
of  its  proteins,  the  peculiar  composition  of  its  in- 
organic content  and  the  remarkable  content  of  the 
dietary  essential,  fat-soluble  A,  in  the  fats  of  milk. 
Milk,  hke  nearly  all  of  the  other  natui^al  foods,  con- 
tains a  great  abundance  of  the  second  dietary  essen- 
tial of  unknown  chemical  nature,  water-soluble  B. 

The  extraordinaiy  value  of  the  proteins  of  milk 
has  been  abundantly  demonstrated  by  experiment. 
]\IcCollmn  ^  conducted  a  series  of  expermients  with 
growing  pigs  to  determme  the  extent  to  which  they 
could  retain  the  protein  of  the  food  for  the  construc- 
tion of  new  body  protem.  The  pig  was  selected  be- 
cause it  is  necessaiy  in  such  studies  to  work  ^^'ith 
an  animal  whose  growth  mipulse  is  as  great  as  pos- 
sible. Only  with  such  species  is  it  to  be  expected 
that  the  animal  \\\\\  utilize  the  proteins  for  gi'owth 
to  the  maximum  extent  made  possible  by  the  chem- 


72      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

ical  character  of  the  food  protein.  The  human 
infant  has  but  httle  growth  hnpulse  because  its 
period  of  infancy  is  long  and  the  adult  size  not  great 
as  compared  with  the  size  at  birth.  A  comparison 
of  the  human  infant  with  the  rat  and  the  young  pig 
(swine)  in  their  capacity  to  grow  in  early  life  is  of 
interest.  The  human  infant  weighs  not  far  from 
seven  pounds  at  birth,  and  during  the  first  year  of 
life  is  ordinarily  able  to  multiply  its  initial  body 
weight  by  three,  for  the  average  weight  at  one  year 
is  about  twenty-one  pounds.  We  may  feed  it  human 
milk  the  entire  time,  or  unmodified  cows'  milk  during 
the  greater  part  of  the  year,  without  in  any  important 
degree  modifying  its  rate  of  growth.  In  the  latter 
case,  we  should  be  supplying  it  with  perhaps  double 
the  amount  of  protein  that  it  would  receive  were  it 
fed  human  milk,  since  the  latter  contains  on  an  aver- 
age about  1.6  per  cent  and  the  former  about  3.5  per 
cent  of  protein. 

In  marked  contrast  to  the  feeble  capacity  of  the 
human  infant  to  store  new  tissue  and  increase  in 
size,  stand  the  rat  and  the  pig.  The  rat  at  birth 
weighs  about  4.83  grams,  and  contains  about  0.064 
grams  of  nitrogen.  At  280  days  of  age  the  male 
should  weigh  about  280  gi^ams,  and  if  moderately 
fat  will  contain  about  8.5  grams  of  nitrogen.  The 
rat  is  able,  therefore,  in  a  period  of  280  days  to 
multiply  its  initial  body  weight  by  about  55, 
and  its  initial  body  nitrogen  content  (protein)  by 
133. 


THE  FOODS  OF  ANIMAL  ORIGIN  73 

The  newborn  pig  weighing  two  pounds  will  con- 
tain about  134  grams  of  dry  matter  and  11.9  gi-ams 
of  nitrogen.  In  280  days  it  may,  if  properly  fed, 
reach  a  weight  of  300  pounds.  It  would  then  have 
a  nitrogen  content  of  not  less  than  2407  grams. 
These  changes  in  size  entail  a  multiplication  of  the 
initial  body  weight  by  150  and  of  the  initial  body 
nitrogen  content  by  202.  The  farm  pig  is  ap- 
parently the  most  rapidly  growing  species  of  land 
animals. 

Such  considerations  determined  the  selection  of  the 
pig  as  a  subject  for  the  test  of  the  biological  value 
of  the  proteins  of  the  various  natural  food-stuffs. 
The  plan  involved  keeping  the  animal  for  a  period 
of  several  days  on  a  diet  free  from  protein,  but  con- 
taining sufficient  starch  to  cover  the  energy  require- 
ments. WTien  the  nitrogen  elimination  in  the  urine 
reached  a  constant  low  level  which  represented  the 
irreducible  minimum,  resulting  from  the  ''wear  and 
tear"  of  the  tissues,  the  animal  was  fed  a  diet  con- 
taining protein  derived  solely  from  a  single  grain, 
or  other  single  food-stuff.  A  record  was  kept  of  the 
intake  of  the  element  nitrogen,  and  of  the  daily  loss 
of  this  element  through  the  excreta,  and  from  these 
records  the  percentage  retained  for  growth  was  ob- 
tained. Similar  experiments  were  carried  out  using 
milk  as  the  sole  source  of  protein.  The  following 
table  smnmaiizes  the  results  obtained. 


74     THE  NE^^^ER  KNOWLEDGE  OF  NUTRITION 

Per  Cent  of  Ingested  Protein  Retained  for  Growth  by 

THE  Pig 

Per  cent  of  ingested 
Source  of  protein  protein  retained 

Corn 20.0 

Wheat 23.0 

Oats  (rolled) 26.0 

Milk 63.0 

The  figures  in  the  table  are  averages  of  a  consider- 
able number  of  results  and  represent  the  general 
trend  of  the  data.  The  experimental  periods  varied 
from  30  to  60  days.  There  can  be  no  doubt  that  the 
proteins  of  milk  are  far  superior  to  those  of  any  foods 
derived  from  vegetable  sources. 

The  problem  of  determining  the  relative  values  of 
the  proteins  of  the  different  foods  when  fed  singly,  sup- 
plemented with  purified  food  additions  that  their  diet- 
ary deficiencies  were  made  good,  was  approached  in 
a  different  way  by  McCoUum  and  Simmonds.^  Rats 
were  fed  diets  in  which  the  protein  was  all  furnished 
by  a  single  natural  food-stuff,  but  the  plane  of  protein 
intake  was  varied  from  very  low  to  higher  intakes,  in 
Older  to  determine  what  was  the  lowest  per  cent  of 
protein  in  the  food  mixture  which  would  just  suffice 
to  maintain  an  animal  without  loss  of  body  weight. 
The  rations  consisted  of  the  following  substances: 

Seed Amount  to  give  the  protein  intake  desired 

Growth-promoting  fat  (butter-fat) 5.0  per  cent 

Suitably  constituted  salt  mixtures 3  to  5  per  cent 

Agar-agar  (to  furnish  indigestible  matter) 2.0  per  cent 

Dextrin To  make  100  per  cent. 


THE  FOODS  OF  ANIMAL  ORIGIN  75 

The  results  showed  that  there  are  indeed  very  great 
differences  in  the  amounts  of  protein  from  different 
seeds,  which  are  necessary  to  maintain  an  animal 
without  loss  of  body  weight.  The  results  for  the 
more  important  seeds  used  as  human  foods  are 
summarized  in  the  follomng  table. 

Table  SH0\\^XG  the  Lowtest  Plane  of  Protein  Intake  De- 
rived FROM  A  Single  Seed  Which  Just  Suffices  to  ]\Iain- 
TAiN  AN  A171MAL  in  Body  Weight,  when  the  Factors 
Other  than  Protein  are  Properly  Constituted 

Source  of  Protein     Plane  of  Protein  Necessary  for  Maintenance 

Milk 3.0  per  cent  of  food  mixture  ^ 

Oat  (rolled) 4.5   "       "       ''     " 

Millet  seed 4.5  '^      "      "    '' 

Maize 6.0  ''      ''      "    " 

Wheat 6.0  "      "      "    " 

Polished  rice 6.0  "      "      "    " 

Flaxseed 8.0  "      "      "    '' 

Na^ybean 12.0"      "      "    '' 

Pea 12.0  "      "      ''     " 

These  maintenance  experiments  were  of  three  to  six  months' 
duration. 

The  data  obtained  with  the  pig  is  seen  to  be  in 
harmony  in  a  general  way  with  those  obtained  with 
the  rat,  and  help  to  substantiate  the  view  which  is 
supported  by  all  the  evidence  available,  viz:  that 
from  the  chemical  standpoint,  the  dietaiy  require- 
ments of  one  species  of  animal  are  the  same  as  those 
of  another.  That  there  are  great  differences  in  the 
physical  characters  of  the  diet  which  suffice  for, 


76     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

or  are  required  by  certain  species  as  contrasted  with 
others,  is  a  matter  of  common  observation.  The 
ruminants  actually  require  coarse  herbage  as  a  part 
of  their  food,  in  order  that  the  aUmentary  tract  may 
function  properly,  whereas  such  physical  properties 
in  the  diet  of  the  omnivora  are  wholly  out  of  place 
beyond  very  limited  amounts. 

In  considering  the  value  of  milk  as  a  constituent  of 
the  diet  it  should  be  borne  in  mind  that  with  respect 
to  the  protein  factor  it  may  enhance  tne  value  of  the 
proteins  of  the  remainder  of  the  food.  It  may  supply 
in  relative  abundance  those  amino-acids  which  are 
present  in  such  smaU  amounts  that  they  form  the 
first,  second,  etc.,  limiting  factors  in  determining  the 
value  of  the  protein  for  growth  or  maintenance,  as 
well  as  by  the  direct  addition  to  the  food  mixture,  of 
the  intrinsically  good  proteins  of  the  milk. 

When  taken  as  the  sole  food  supply  by  the  adult, 
milk  is  very  liable  to  produce  constipation  and  be- 
cause of  its  high  protein  content,  may  lead  to  the  ex- 
cessive development  of  putrefactive  bacteria  in  the 
intestine.  The  cages  of  rats  fed  solely  on  milk  de- 
velop an  offensive  odor.  The  addition  of  carbohy- 
drate, such  as  starch  or  certain  of  the  sugars,  tend 
to  cause  the  disappearance  of  the  obnoxious  flora  from 
the  alimentary  tract,  and  the  development,  instead, 
of  types  which  do  not  produce  injurious  decomposi- 
tion products  in  their  action  on  proteins. 

Meats. — The  muscle  tissue  of  an  animal  con- 
sists of  highly  specialized  tissue  whose  chief  function 


THE  FOODS  OF  ANIMAL  ORIGIN  77 

is  to  produce  mechanical  work  through  contraction. 
It  is  in  addition  a  storage  organ  in  which  glycogen, 
a  form  of  starch,  and  also  fats  are  stored  as  reserve 
foods.  It  contains  but  httle  of  cellular  structures  in 
the  sense  that  the  glandular  organs,  such  as  the 
liver,  kidney,  pancreas,  etc,  do.  Chemical  analysis 
shows  the  muscle  to  consist,  aside  from  the  reserve 
food-stuffs,  prmcipally  of  water,  protein  and  salts. 
The  glandular  organs  yield  a  high  content  of  nucleic 
acid,  while  the  muscle  tissue  yields  but  little  in  pro- 
portion to  its  weight.  The  inorganic  content  of  the 
muscle  tissue  resembles  that  of  the  seed  of  the  plant, 
rather  than  the  leaf  both  in  amount  and  in  the  rel- 
ative proportions  among  the  elements. 

Corresponding  with  the  specialized  function,  and 
the  peculiarities  in  composition  just  mentioned,  we 
find  that  its  dietary  properties  are  comparable 
with  the  seed  rather  than  the  leaf.  In  fact,  muscle 
tissue  differs  markedly  from  the  seed  in  only  one 
respect,  when  considered  as  a  food-stuff,  viz.,  in  the 
quality  of  its  proteins.  These  are  distinctly  better 
than  those  of  the  seeds  with  which  investigations 
have  been  conducted.  The  inorganic  content  must 
be  supplemented  by  the  sam.e  inorganic  additions  as 
the  seed,  and  the  muscle  proves  to  be  relatively  poor 
in  its  content  of  the  unidentified  dietary  essential 
fat-soluble  A,  as  compared  with  such  foods  as  milk, 
egg  yolk  and  the  leaves  of  plants. 

Smce  the  inorganic  part  of  muscle  resembles  that 
of  the  seed,  except  that  the  latter  is  poorer  in  iron 


78     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

and  it  is  low  in  its  content  of  fat-soluble  A,  it  does 
not  supplement  the  seeds  in  an  appreciable  degree 
other  than  with  respect  to  the  protein  factor.  It 
follows,  therefore,  that  we  should  not  expect  to  se- 
cure growth  and  normal  nutrition  with  mixtures  of 
seeds,  and  meat  and  experimental  trials  demonstrate 
that  this  is  the  case.  Mixtures  of  meat  (muscle) 
and  seeds  require  to  be  supplemented  with  respect 
to  sodium,  calcium  and  chlorine,  just  as  do  seed  mix- 
tures alone^.  The  fat-soluble  A  content  of  such 
iiiLxtures,  unless  millet  seed  is  one  of  the  seeds  pres- 
ent to  the  extent  of  25  per  cent,  must  be  increased 
by  suitable  additions  before  the  optimum  nutrition 
can  be  attained,  and  the  animals  can  successfully 
bear  the  strain  of  reproduction  and  lactation.  Meats 
are,  therefore,  but  partial  supplementary  foods  when 
employed  w^ith  the  seeds  or  the  products  prepared 
from  seeds,  such  as  wheat  flour,  corn  meal,  polished 
rice,  etc.  Such  diets  can  be  partially  corrected  by 
the  liberal  use  of  leafy  vegetables,  but  better  by  the 
use  of  the  latter  along  wdth  milk. 

The  pronounced  deficiencies  of  m.uscle  tissue  as  a 
food-stuff,  naturally  suggests  the  question  of  the 
reason  for  the  success  of  the  nutrition  of  the  strictly 
carnivorous  animals.  The  explanation  is  found  in 
the  order  in  which  such  creatures  select  the  parts  of 
the  carcasses  of  their  prey.  The  larger  carnivorse, 
after  striking  down  an  animal,  immediately  open  the 
large  veins  of  the  neck  and  suck  blood  as  long  as  it 
flows.    Their  second  choice  of  tissues  is  the  Uver,  and 


THE  FOODS  OF  ANIMAL  ORIGIN  79 

following  this  the  other  glandular  organs.  Muscle 
tissue  is  only  eaten  aftez'  these  have  been  consumed. 
With  such  a  selection  the  animal  secures  eveiything 
which  it  needs  for  its  nutrition  except  a  sufficient 
amount  of  calcium,  and  this  is  obtained  througli 
gnawing  off  the  softer  parts  of  the  extremities  of  the 
bones.  The  failure  of  many  carnivora  to  thrive  w^hen 
confined  in  zoos,  it  probably  the  result  of  their  being 
fed  too  largely  upon  muscle  tissue  and  bones.  They 
should  be  supplied  with  an  abundance  of  the  gland- 
ular organs  and  with  blood  to  make  then  diet  com- 
plete. With  rats  McCollum,  Simmonds  and  Parsons 
have  observ^ed  fairly  satisfactory  grow^th  on  equal 
parts  of  muscle  tissue  (round  steak)  and  dried 
blood,  whereas  either  of  these  alone  cannot  induce 
growth.^ 

The  Glandular  Organs. — The  liver  and  kidney 
may  serve  as  typical  examples  of  the  glandular  or- 
gans which  are  employed  as  foods.  There  are  cer- 
tain organs  of  internal  secretion,  such  as  the  thy- 
roid, and  suprarenal  glands  w^hich  elaborate  products 
w^hich  are  highly  active  pharmacological  agents,  and 
the  liberal  use  of  these  glands  as  food  would  lead  to 
disastrous  consequences.  The  glands  contain  but  lit- 
tle of  the  inorganic  elements  in  which  the  seeds  are 
deficient.  Their  proteins  are  probably  of  excellent 
quality,  but  have  not  yet  been  carefully  investigated. 
The  glands  consist  largely  of  actively  functioning 
cells,  having  specialized  functions,  and  accordingly 
they  prove  to  contain  a  more  liberal  amount  of  both 


80      THE  NKWER  KNOWLEDGE  OF  NUTRITION 

the  fat-soluble  A  and  water-soluble  B  than  does  the 
muscle.  In  respect  to  the  former  of  the  unidentified 
dietary  essentials  the  glandular  organs  surpass  the 
seeds  in  value/  From  this  description  it  will  be 
seen  that  the  glandular  organs  approximate  more 
closely  complete  foods  than  does  the  muscle,  but 
it  is  likewise  apparent  that  these  tissues  do  not 
form  efficient  supplements  for  the  seeds  and  their 
products. 

Eggs. — The  egg  contains  all  the  chemical  com- 
plexes necessaiy  for  the  formation  of  the  chick  dur- 
ing incubation.  The  egg  is  therefore  to  be  expected 
to  furnish  everything  which  is  needed  for  the  nutri- 
tion of  a  mammal,  for  as  has  been  already  stated, 
the  evidence  all  supports  the  beUef  that  the  chemical 
requirements  of  one  species  are  the  same  as  another. 
The  egg  is  indeed  a  complete  food,  but  not  one  which 
produces  the  optimum  results  when  employed  as 
the  sole  source  of  nutriment.  Aside  from  the  calcium 
content  of  the  white  and  yolk  of  the  egg,  which  is 
much  lower  than  that  of  milk,  the  contents  of  the  egg 
resemble  milk  in  a  general  way  in  nutritional  value. 
The  high  content  of  milk  sugar  in  the  latter,  and  the 
almost  complete  absence  of  carbohydrate  from  the 
egg,  cause  them  to  differ  considerably  in  the  physi- 
ological results  which  they  produce  on  animals  when 
each  is  fed  as  the  sole  source  of  nutriment.  Egg, 
when  fed  alone,  encourages  much  more  than  milk 
the  development  of  putrefactive  organisms  in  the 
aUmentary   tract.     The  shell   of   the   egg  consists 


THE  FOODS  OF  AXHIAL  ORIGIN  81 

principally  of  calcium  carbonate,  and  during  in- 
cubation this  is  to  some  extent  dissolved  and  ab- 
sorbed for  the  formation  of  the  chick.  AYhen  eggs 
serve  as  human  food  the  shells  are  discarded.  There 
are  distinct  differences  in  the  chemical  natm-es  of 
the  constituents  of  eggs  as  contrasted  with  milk. 
The  principal  protem  of  egg  yolk,  like  that  of  milk, 
contains  phosphorus,  but  the  fats  of  milk  are  phos- 
phorus free,  whereas  phosphorized  fats  (e.  g.,  leci- 
thins) are  very  abundant  in  egg  fats.  There  is  an 
abundance  of  lactose  in  milk,  whereas  the  egg  con- 
tains but  a  trace  of  sugar.  These  differences  have 
Kttle,  if  any,  diefcar>^  significance.  The  yolk  is  es- 
pecially rich  in  both  the  fat-soluble  A  and  water- 
soluble  B.  With  the  exception  of  milk  the  foods  of 
animal  origin  do  not  supplement  completely  the  diet- 
ary deficiencies  of  the  seeds  and  their  products. 

We  are  now  able  to  make  certain  generalizations 
of  fundamental  miportance  regarding  the  t^-pes  of 
combinations  of  the  natural  food-stuffs  which  may 
be  expected  to  give  good  results  m  the  nutrition  of 
an  annual . 

(1)  Seed  mixtures,  no  matter  how  complex,  or 
from  w^hat  seeds  they  are  derived,  ^^'ill  never  induce 
optimum  nutrition. 

Seeds  with  tubers,  or  seeds  with  tubers,  roots  and 
meat  (muscle)  ^^ill  in  all  cases  fail  to  even  approxi- 
mate the  optimum  in  the  nutrition  of  an  animal 
during  growth. 

(2)  The  only  successful  combinations  of  natural 


82      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

foods  or  milled  products  for  the  nutrition  of  an  ani- 
mal are: 

(a)  Combinations  of  seeds,  or  other  milled 
products,  tubers  and  roots,  either 
singly  or  collectively  taken  with  suf- 
ficient amounts  of  the  leaves  of  plants. 

(b)  Combinations  of  the  food-stuffs  enu- 
merated under  (a)  taken  along  with  a 
sufficient  amount  of  milk  to  make  good 
their  deficiencies. 

Milk  and  the  leaves  of  plant  are  to  he  regarded  as 
protective  foods  and  should  never  he  omitted  from  the 
diet.  Milk  is  a  hetter  protective  food  than  are  the  leaves, 
when  used  in  appropriate  amounts. 

It  should  be  appreciated  that  not  all  diets  which 
conform  to  the  requirements  laid  dowTi  in  the  above 
generalizations,  will  give  equally  good  results.  This 
is  especially  true  of  diets  of  the  type  under  (2). 
Chart  6  shows  the  great  differences  in  the  food 
values  of  a  few  mixtures  of  seeds  and  leaves.  It  can 
be  stated  definitely,  however,  that  diets  which  are 
not  made  up  according  to  the  second  plan,  will 
never  be  satisfactory. 


CHAPTER  V 

THE   DISEASES   REFERABLE    TO    FAULTY   DIET,    OR   THE 
SO-CALLED    '^DEFICIENCY   DISEASES" 

It  has  been  pointed  out  that  in  the  year  1911  Funk 
took  up  the  study  of  the  disease  beri-beri.  He  made 
use  of  the  observation  of  Eijkman,  that  the  symp- 
toms could  be  produced  expermientally  in  birds  by 
feeding  them  exclusively  upon  polished  rice  for  two 
to  four  weeks,  whereas  birds  remain  for  much  longer 
periods  in  a  state  of  health  when  fed  exclusively  upon 
the  unpohshed  grain.  He  also  made  use  of  the  ob- 
servation of  Fraser  and  Stanton,  that  an  alcohoUc 
extract  of  rice  polishings  would  effect  a  ''cure"  of 
pol^^ieuritic  birds.  Funk  made  nmnerous  elaborate 
and  painstaking  attempts  to  separate  the  "curative" 
substance,  and  wrote  extensively  on  what  he  believed 
to  be  "deficiency"  diseases.  Under  this  term  he 
included  beri-beri,  scur^T)  pellagra  and  rickets. 
Hopkins  discovered  that  small  additions  of  milk 
to  food  mixtures  composed  of  purified  protein, 
carbohydrate,  fats  and  inorganic  salts,  rendered  them 
capable  of  inducing  growth,  whereas  without  such 
additions  no  growth  could  be  secured.  The  effects 
were  out  of  all  proportion  to  the  energ^^,  or  protein 
value  of  the  added  milk,  and  he  suggested  the  exist- 

83 


84      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

ence  of  '' accessory"  food-stuffs,  which  are  required 
in  but  small  amounts,  and  which  are  absent  from  the 
mixtures  of  purified  food-stuffs,  which  fail  to  promote 
growth.  To  the  supposed  '^curative"  substances, 
the  presence  of  which  in  the  diet  prevents  the  develop- 
ment of  several  syndromes  enumez^ated.  Funk  gave 
the  collective  name  ^Sdtamines."  Thus  he  distin- 
guished an  antineuritic  ^^vitamine,"  an  antiscorbutic 
'Sdtamine,"  etc.  These  supposed  substances  have 
since  been  variously  designated  as  '^growth  sub- 
stances," ^^ growth  determinants,"  ^^food  hormones," 
''accessory"  food  substances,  etc. 

McCollum  and  Davis  through  their  studies  wdth 
diets  of  purified  food-stuffs,  pointed  out  that  it  was 
highly  probable  that  there  are  essential  in  the  diet 
but  two  substances  rather  than  groups  of  substances 
of  imknoTVTL  chemical  nature,  and  it  was  sho\\Ti,  as 
has  been  pointed  out,  that  one  of  them  is  associated 
with  certain  fats,  while  the  other  is  never  found  with 
the  isolated  fats  of  either  animal  or  vegetable  origin. 
McCollum  and  Kennedy  ^  suggested  that  they  be 
provisionally  called  fat-soluble  A  and  water-soluble 
B,  because  of  their  characteristic  solubihty  in  fats 
and  in  water  respectively. 

The  above  terms,  except  the  last  two,  are  mis- 
nomers. The  word  accessory,  carries  the  idea  that 
the  substances  in  question  are  dispensable.  Con- 
diments may  be  desirable,  but  they  can  be  dispensed 
with,  and  are  properly  designated  as  accessory  food 
substances.    An  indispensable  food  complex  cannot 


''DEFICIENCY"  DISEASES  85 

properly  be  designated  by  this  term.  ^^Vitamine" 
is  objectionable,  because  the  prefix  vita  connotes  an 
importance  of  these  dietary  essentials  greater  than 
other  equally  indispensable  constituents  of  the  diet, 
such  as  certain  of  the  amino-acids  which  play  a  role 
in  protein  metaboUsm.  The  ending  amine  has  a 
definite  and  specific  meaning  in  organic  chemistry, 
being  used  to  designate  a  compoimd  derived  from 
ammonia  by  the  substitution  of  one  or  more  of  its 
h^^drogen  atoms  by  various  organic  radicals.  Any 
substance  to  be  properly  designated  as  amine  must 
contain  the  element  nitrogen.  There  is  no  e\ddence 
that  either  of  these  unidentified  dietary  essentials 
is  an  amine,  and  indeed  fat-soluble  A  probably  con- 
tains no  nitrogen,  for  it  is  especially  abundant  in 
butter  fat,  and  the  latter  is  practically  free  fix)m  this 
element. 

^'Food  hormones"  is  an  objectionable  term,  be- 
cause all  the  evidence  available  indicates  that  both 
the  fat-soluble  A  and  water-soluble  B  are  never- 
faihng  constituents  of  the  cells  of  both  annual  and 
plant  tissues.  They  have  nothing  in  common  with 
the  hormones.  The  latter  are  chemical  substances 
which  are  formed  in  the  body  by  special  tissues  and 
contributed  to  the  blood  stream  where  they  cause 
the  stimulation  of  certain  other  tissues  to  physiolog- 
ical activity.  They  are  chemical  messengers,  wliile 
the  substances  under  discussion  are  food  complexes, 
apparently  necessary  for  all  the  living  cells  of  the 
body.    It  has  been  pointed  out  that  the  content  of 


86      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

both  of  these  two  dietao'  essentials  appears  to  rim 
parallel  to  the  content  of  cellular  elements  m  the 
food-stuffs,  regardless  of  their  source. 

'^Growth  substances"  and  '^ growth  determinants" 
are  not  good  terms  for  the  reason  that  the  substances 
in  question  are  just  as  essential  for  the  maintenance 
of  a  full  grown  animal  in  a  state  of  health  as  they  are 
for  the  support  of  growth  in  the  young.  Further- 
more, in  actual  experience,  rations  are  found  in 
which  the  content  of  one  or  more  essential  amino- 
acids  are  present  in  such  amounts  that  they  form 
the  limiting  factor  which  determines  the  value  of  the 
ration .  It  is  easy  to  prepare  a  food  mixture  in  which 
any  one  of  the  eight  or  nine  essential  inorganic 
elements  which  the  diet  must  furnish,  wdll  be  so  low 
as  to  prevent  the  growth  of  an  animal  even  though 
the  food  is  otherwise  of  satisfactory  character.  In 
one  case  the  addition  of  a  suitable  sodium  compound 
or  in  another  a  calcium  or  a  potassium  salt  might 
induce  growth,  and  these  elements  might,  with  just 
as  much  propriety,  be  called  ^'growth  determinants" 
as  to  apply  this  telm  to  one  of  the  still  unidentified 
food  essentials.  The  term  might  fittingly  be  appHed 
to  any  of  the  indispensable  components  of  the  diet, 
such  as  certain  of  the  amino-acids,  which  result  from 
the  digestion  of  the  proteins. 

All  natural  food-stuffs,  such  as  the  seeds  of  plants, 
the  leafy  vegetables,  fruits,  roots,  tubers,  meats, 
eggs  and  milk,  contain  certain  amounts  of  all  the 
substances  which  are  indispensable  components  of 


"DEFICIENCY"  DISEASES  87 

the  diet.  There  is,  however,  great  variation  in  the 
quality  of  the  different  foods  with  respect  to  the  sev- 
eral factors.  Some  contain  much  protein,  others 
httle,  and  a  similar  variation  mth  respect  to  other 
constituents  is  found.  The  special  properties  of  the 
several  groups  of  food-stuffs  have  been  described  in 
Chapters  III  and  IV. 

The  best  sources  of  fat-soluble  A  are  whole  milk, 
butter  fat  and  egg  yolk  fats  and  the  leaves  of  plants. 
The  seeds  of  plants  contain  less  and  those  products 
derived  from  the  endosperm  of  the  seed  are  very 
poor  in  this  substance.  Such  food-stuffs  as  bolted 
flour,  degerniinated  corn  meal,  polished  rice,  starch, 
glucose  and  the  sugars  from  milk,  cane,  and  beet  are 
practically  free  fx^om  the  fat-soluble  A.  The  specific 
result  of  a  lack  of  a  sufficient  amount  of  this  sub- 
stance in  the  diet  is  the  development  of  a  condition 
of  the  eyes  which  appears  to  be  rightly  classed  as  a 
tr^-pe  of  xerophthabiiia.  The  eyes  become  swollen 
so  badly  that  they  are  opened  with  difficulty  or  not 
at  all.  The  cornea  becomes  inflamed,  and  unless 
the  missing  dietary  essential  is  supplied,  blindness 
speedily  results.  Osborne  and  Alendel  ^  have  also 
noted  this  condition  in  exi^erimental  animals  and 
its  relief  by  feeding  butter  fat.  The  introduction 
into  the  diet  of  5  or  more  per  cent  of  butter  fat 
will  cause  prompt  recovery  in  cases  w^here  the  an- 
imals are  within  a  few  days  of  death.  Complete  re- 
covery takes  place  within  two  weeks  if  the  sight  has 
not  been  destroyed.     The  normal  condition  of  the 


88      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

eyelids  can  be  restored  even  after  the  sight  is  gone 
and  the  cornea  has  faded. 

WTien  the  diet  consists  principally  of  one  of  the 
cereal  grains  such  as  the  wheat,  oat  or  corn  kernel, 
or  even  a  mixture  of  these,  and  it  is  satisfactorily 
supplemented  with  respect  to  the  inorganic  elements 
in  which  they  are  deficient,  viz.,  calcium,  sodium 
and  chlorine,  and  their  proteins  are  enhanced  in 
value  by  the  addition  of  a  protein  of  good  quality, 
animals  restricted  to  such  a  food  supply  may  long 
escape  the  onset  of  this  disease.  The  seeds  are  not 
entirely  lacking  in  the  substance,  fat-soluble  A. 
They  contain,  especially  the  wheat  and  corn  kernels, 
about  half  the  amount  required  to  maintain  an 
animal  in  a  state  of  health.  If  the  seeds  or  their 
mixtures  are  supplemented  with  respect  to  but  a 
single  dietary  factor,  e.  g.  inorganic  salts,  but  the 
protein  content  is  left  of  relatively  low  biological 
value,  the  debilitating  effects  of  the  low  value  of  the 
food  mixture  in  the  two  dietary  factors  (protein  and 
fat-soluble  A)  simultaneously  will  hasten  the  onset 
of  xerophthalmia.^  When  judging  the  effects  of  the 
diet  on  an  animal,  it  is  necessary  to  take  into  account 
the  fact  that  the  diet  is  a  complex  thing,  and  that  if 
it  is  properly  constituted  with  respect  to  all  factors 
but  one  an  animal  may  tolerate  it  without  apparent 
injury  whether  the  fault  lies  in  one  or  another  of  the 
essential  components.  The  value  of  one  component 
m^ay  fall  well  below  that  which  will  lead  to  serious  mal- 
nutrition, when  a  second  dietary  factor  is  likev/ise  poor. 


"DEFICIENCY"   DISEASES  89 

The  idea  should  not  be  entertained  that  butter 
fat  is  the  only  food  which  supplies  the  fat-soluble  A. 
If  the  diet  contains  a  liberal  amount  of  milk,  eggs, 
glandular  organs  or  the  leaves  of  plants,  it  wdU,  if 
otherwise  satisfactorily  constituted,  prevent  the 
onset  of  the  eye  disease.  The  seeds  and  seed  prod- 
ucts, such  as  wheat  flour  (bolted),  degerminated 
corn  meal,  polished  rice,  starch,  the  sugars,  s>Tups, 
tubers,  roots,  such  as  the  radish,  beet,  carrot,  tui-nip, 
etc.,  and  also  the  muscle  tissue  of  animals,  such  as 
ham,  steak,  chops,  etc.,  do  not  contain  enough  of 
the  fat-soluble  A  to  be  classed  as  important  somxes 
of  this  dietary  essential.  The  tubers  and  roots 
appear  to  be  somewhat  richer  in  it  than  ai-e  the 
seeds. '^  In  the  form  in  which  they  are  ordinai^ily 
eaten,  as  mashed  or  baked  potato,  baked  sweet 
potato,  fresh  or  creamed  radish,  cooked  carrots, 
beets  or  creamed  turnips,  the  water  content  of  the 
dish  as  served  is  so  high  that  the  amount  of  soUds 
eaten  is  not  a  very  high  per  cent  of  the  total  food 
supply,  and  the  protective  action  is  correspondingly 
limited.  In  America,  however,  potatoes  are  seldom 
eaten  without  the  addition  of  butter.  The  vegetable 
fats  and  oils  such  as  olive  oil,  cottonseed  oil,  peanut 
and  cocoanut  oils,  although  good  energy  yielding 
foods,  do  not  furnish  this  dietary  essential.  The 
body  fats  of  animals  such  as  lard,  beef  fat,  etc.,  are 
not  important  sources  of  the  fat-soluble  A. 

McCollum  and  his  co-w^orkers  have  repeatedly 
observed  in  experimental  animals  the  type  of  xeroph- 


90      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

thalmia  of  dietary  origin  which  has  been  described 
above.  They  have  many  times  rescued  animals 
from  the  thi^eshold  of  death  by  the  addition  of 
butter  fat  to  the  diets  of  the  animals  which  were 
suffering  from  the  disease  which  was  brought  about 
by  a  lack  of  a  sufficient  amount  of  the  fat-soluble  A 
in  their  food.  It  is  important  to  inquire  whether 
or  not  this  disease  has  ever  occurred  in  man.  It  is 
not  easy  to  decide  from  the  descriptions,  in  the  clin- 
ical literature,  of  the  eye  troubles  of  poorly  nourished 
peoples  in  various  parts  of  the  world,  which  are  of 
the  peculiar  tyipe  w^ith  which  we  are  now  dealing, 
and  which  are  due  to  other  causes.  Soreness  of  the 
eyes  is  common  among  many  primitive  peoples. 
Herdlika  ^  describes  severe  eye  troubles  among  the 
American  Indians  of  the  southwest,  and  attributed 
them  to  too  great  exposure  to  strong  sunlight.  In- 
fection of  the  eyes  is  common  among  many  peoples, 
and  the  clinician,  not  being  aware  of  the  existence 
of  a  pathological  condition  of  the  eyes  due  to  faulty 
diet,  would,  of  course,  be  inclined  to  attribute  such 
conditions  to  other  causes. 

There  are  several  instances  of  the  occurrence  of 
conditions  described  in  the  Uterature  as  xerophthal- 
mia, which  seem  to  be  beyond  question,  cases  in 
which  the  disease  has  occurred  in  man  as  the  result 
of  specific  starvation  for  the  dietary^  essential,  fat- 
soluble  A.  Mori  ^  in  Japan  described  in  1904,  four- 
teen hundred  cases  of  xerophthalmia  among  children 
in  a  time  of  food  shortage.    He  describes  the  condi- 


■  .22  .2  ^ 
S    o  .22  ^ 


k-^         ^^         L^         /— \ 


3 
C3 


43 
bO 


^     O     bC 

5l    o    fl 


"DEFICIENCY"   DISEASES  91 

tion  in  a  manner  which  agrees  closely  with  that  which 
McCollmn  and  Sininioiids  have  observed  in  animals 
whose  diets  were  lacking  in  a  sufficient  amount  of 
fat-soluble  A.  The  eAddence  that  he  was  dealing 
with  this  disease  is  made  almost  conclusive  by  the 
fact  tliat  he  states  that  feedmg  chicken  livers  effected 
a  cure.  It  has  been  alx'eady  mentioned  that  the 
glandular  organs  contain  the  fat-soluble  A  in  fanly 
liberal  amounts.  The  Japanese  have,  as  a  rule,  no 
dairy  products.  Their  diet  consists  of  seeds  and 
seed  products,  roots,  tubers,  leaves  and  meats,  prin- 
cipally fish.  Their  principal  sources  of  the  dietaiy 
factor  in  question  are  the  leafy  vegetable  and  eggs,  the 
former  of  which  in  normal  times  they  consume  much 
larger  amounts  than  do  the  peoples  of  most  j^arts 
of  Europe  and  America.  Shortage  of  food  will  occur 
usually  owing  to  drought,  and  the  first  products 
which  fail  are  the  green  vegetables,  and  accordingly 
the  dietary  essential  which  would  be  least  abundant 
would  be  the  fat-soluble  A.  ]\Iori  attributed  the 
xerophthahnia  to  fat  starvation.  It  seems  highly 
probable,  how^ever,  that  a  lack  of  fat  w^as  not  in  it- 
self the  cause  of  the  disease,  but  rather  the  lack  of 
the  unidentified  dietary  essential  which  is  associated 
with  certain  fats,  but  is  not  furnished  by  any  of  the 
isolated  fats  of  vegetable  origin,  although  it  is  present 
in  plant  tissues  where  these  contam  cellular  struc- 
tures. Mori  states  that  the  disease  does  not  occur 
among  fisher  folk. 

Bloch  '  has  recently  described  forty  cases  of  severe 


92     THE  NEWER  KNOWLEDGE  OF  NUTRITION 

necrosis  of  the  cornea  with  ulceration,  in  the  vicinity 
of  Copenhagen.  The  children  had  been  fed  nearly 
fat-free  separator  skim  niilk,  and  were  atrophic  or 
dystrophic  and  anemic.  He  attributed  the  disorder 
to  fat  starvation,  since  the  children  responded  with 
recovery  when  fed  breast  milk,  or  in  the  case  of  older 
ones,  with  whole  milk  mixtures  and  to  codliver  oil 
administration.  The  recovery,  it  will  be  noted, 
followed  the  feeding  of  those  substances  which  are 
good  sources  of  the  fat-soluble  A. 

Czerny  and  Keller  ^  describe  a  similar  condition  of 
the  eyes  in  children  suffering  from  malnutrition  as 
the  result  of  being  restricted  to  a  cereal  diet. 

It  seems  certain  that  these  cases  of  xerophthalmia 
should  be  looked  upon  as  a  ^^ deficiency  disease" 
not  hitherto  recognized  in  its  proper  relation  to  diet. 
It  is  not  a  fat  starvation,  but,  if  it  be  the  same  condi- 
tion w^hich  McCollum  and  Simmon ds  have  definitely 
shown  to  be  readily  relieved  in  its  early  stages  by 
the  administration  of  such  foods  as  contain  liberal 
amiounts  of  fat-soluble  A,  it  would  not  be  relieved 
by  feeding  with  vegetable  fats  in  any  amounts.  Milk, 
eggs,  leafy  vegetables  and  the  glandular  organs, 
are  the  foods  which  serve  to  protect  against  a  short- 
age of  this  indispensable  dietary  component.  This 
type  of  xerophthalmia  is  analogous  to  beri-beri,  in 
that  it  is  due  to  the  lack  of  a  specific  substance  in 
the  diet.  Beri-beri  and  xerophthalmia  are  according 
to  McCollum  and  Simmonds,  the  only  diseases  refera- 
ble to  faulty  diet,  which  are  to  be  explained  inthis  way. 


"' DEFICIENCY"   DISEASES  93 

Beri-beri  is  a  disease  common  in  the  Orient  among 
peoples  who  Umit  their  diet  largely  to  polished  rice 
and  fish.  It  has,  in  recent  years,  been  described  in 
Laborador  owing  to  excessive  consumption  of  bolted 
flour, ^  and  in  Brazil  among  laborers  whose  diets  were 
of  varied  character,  but  not  judiciously  chosen. ^^ 
It-  most  strikmg  characteristic  is  a  general  paralysis, 
and  it  is  frequently  referred  to,  especially  when  pro- 
duced experimentally  in  animals,  as  pol^meuritis. 

The  disease  was  first  produced  in  animals  by 
Eijkman  ^^  in  1897.  He  discovered  that  when 
pigeons  and  chickens  were  restricted  to  a  diet  of 
polished  rice,  they  steadily  lost  weight  and  in  time 
came  to  manifest  all  the  essential  symptoms  char- 
acteristic of  beri-beri  in  man.  In  pigeons  the  disease 
usually  appears  in  two  or  three  weeks.  He  found 
that  feeding  rice  pohshings  would  produce  a  relief 
of  the  symptoms.  This  result  suggested  that  there 
was  lacking  from  polished  rice,  something  which  was 
necessary  for  the  maintenance  of  health  in  the  bird, 
and  that  that  something  was  present  m  the  rice 
polishing?.  This  was  the  first  experimental  evidence 
that  there  is  necessary  in  the  diet  substances  other 
than  proteins,  carbohydrates,  fats  and  inorganic  salts. 

The  observations  of  Eijkman  attracted  but  little 
attention  until  Funk  ^-  took  up  the  study  of  beri- 
beri in  1910.  Fraser  and  Stanton  had,  as  early  as 
1907,  employed  alcoholic  extracts  of  rice  polishings 
for  the  cure  of  experimental  pol^meuritis.  Funk 
made  numerous  studies  directed  toward  the  isolation 


94      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

and  study  of  the  substance  which  exerts  the  curative 
effect,  and  developed  in  his  writings  the  well-knowna 
''vitamine"  hyj^othesis.  This  hypothesis  postulated 
the  existence  of  a  similar  protective  substance  for 
each  of  the  diseases  scurvy,  pellagra  and  rickets, 
in  addition  to  that  which  in  the  normal  diets  pro- 
tects against  beri-beri. 

Funk  had  experimental  evidence  in  support  of  his 
theory  only  in  the  case  of  beri-beri.  The  evidence 
that  the  other  diseases  which  he  included  in  the 
category  of  '^deficiency"  diseases  are  due  to  the  lack 
of  specific  complexes,  was  of  the  nature  of  clinical 
observations,  rather  than  well  controlled  experiments. 
The  peculiar  value  of  butter  fat  was  unknown  to 
him,  and  he  classed  it  among  the  food  substances 
which  contain  no  ^^vitamine"  because  its  administra- 
tion to  polynemitic  pigeons  produced  no  beneficial 
effects.  ^^  Funk  deserves  great  credit  for  the  evidence 
which  he  secured  that  the  amount  of  the  substance 
which  can  be  extracted  from  rice  polishings,  which  is 
necessary  to  cause  the  relief  of  polyneuritis  in  a 
pigeon,  is  exceedingly  small.  A  few  milligrams  of 
material  which  is  still  contaminated  with  impurities 
suffices  to  bring  about  relief  in  a  bird  which  is  in  a 
helpless  condition  and  within  a  few  hours  of  death, 
and  to  make  it  appear  like  a  normal  pigeon.  The 
effects  seem  to  be  out  of  all  proportion  to  the  amount 
of  substance  administered.  Funk's  studies  were  con- 
firmed and  extended  by  the  im.portant  work  of 
Williams.  1^ 


"DEFICIEXCY"   DISEASES  95 

Thei^e  can  be  no  doubt  that  there  are  two  ^' de- 
ficiency'" diseases  in  the  sense  in  which  Funk  and 
his  school  employed  this  term.  One  of  these  is 
beri-beri  and  the  other  the  t^'pe  of  xerophthabiiia 
which  ]\IcCollimi  and  Sunmonds  have  pointed  out 
as  occurring  occasionally  in  man  as  the  result  of 
faulty  diet,  and  have  demonstrated  to  be  the 
same  condition  which  results  in  annuals  as  the  re- 
sult of  specific  starvation  for  the  unidentified  di- 
etary essential  fat-soluble  A.  It  is  of  the  greatest 
miportance  to  determine  whether  scur\y,  pellagra 
and  possibly  rickets  are  likewise  to  be  attributed  to 
the  lack  of  snnilar  substances  of  a  specific  nature  in 
the  diet.  It  has  already  been  mentioned  in  Chapter 
II  that  from  a  knowledge  of  the  dietary  properties 
of  the  oat  kernel,  ]McCollum  and  Pitz  concluded 
from  a  study  of  experimental  scur\y  in  the  guinea 
pig,  that  this  disease,  while  referable  to  faulty  diet, 
does  not  result  from  the  absence  of  any  special  sub- 
stance from  the  diet.  The  evidence  upon  which  this 
conclusion  rests  has  been  touched  upon  (page  36) 
and  will  be  next  briefly  considered. 

The  oat  kernel,  when  submitted  to  the  biological 
method  of  analysis  described  in  the  first  chapter,  was 
found  to  contain  all  the  chemical  elements  and  com- 
plexes necessar}^  for  the  promotion  of  gi'owth  and 
health  in  a  mammal,  but  not  in  suitable  proportions. 
Like  other  seeds  it  requires  certain  inorganic  addi- 
tions, and  its  content  of  the  unidentified  fat-soluble 
A  is  enthely  too  small  to  pennit  of  growth,  or  to 


9G      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

protect  an  animal  against  the  eye  disease,  xeroph- 
thalmia. In  addition,  its  proteins  are  not  com- 
parable in  value  with  those  of  such  foods  as  milk, 
eggs  and  meats.  The  important  fact  was  demion- 
strated  by  McCollum,  Simmonds  and  Pitz,  that 
if  the  extracts  of  natural  foods  which  we  have  long  em- 
ployed in  our  experimental  work  and  which  we  desig- 
nate water-soluble  B,  contain  any  physiologically  in- 
dispensable substance  other  than  that  which  prevents 
heri-beri,  the  oat  kernel  contains  all  of  these.  This 
follows  from  the  fact  that  they  were  able  to  induce 
normal  growth  and  prolonged  well-being  in  animals 
fed  the  oat  kernel  supplemented  only  with  purified 
food  substances, — viz:  protein  and  inotganic  salts, 
and  a  growth-promoting  fat.  The  latter  term 
is  used  to  designate  a  fat  containing  the  fat- 
soluble  A. 

McCollum  and  Pitz  observed  that  the  guinea  pig 
suffers  from  scurvy,  not  only  when  restricted  to  a 
diet  of  oats,  as  stated  by  Hoist,  but  likewise  when  fed 
oats  and  all  the  fresh  milk  it  wdll  consume.  Jackson 
and  Aloore  ^^  made  this  observation  independently 
and  described  it  sev^eral  months  previous,  in  their 
excellent  studies  of  the  bacteriology^  of  the  digestive 
tract  and  tissues  of  the  guinea  pig,  after  the  anim.als 
have  developed  the  disease  as  the  result  of  an  ex- 
clusive oat  and  malk  diet.  Milk  alone  is  a  complete 
food,  and  suffices  for  the  maintenance  of  growth  and 
a  good  state  of  nutitrion  in  several  species  of  animals, 
such  as  the  rat  and  swine.    It  cannot,  therefore,  be 


"DEFICIENCY"   DISEASES  97 

lacking  in  any  unidentified  food  substance.  WTiy, 
then,  should  the  guinea  pig  suffer  scurvy  when  re- 
stricted to  a  diet  of  oats  and  niilk? 

]McColhun  and  Pitz  found  in  the  guinea  pigs  which 
had  died  of  scurv^y^  that  the  cecum  which  is  a  very 
large  and  very  dehcate  pouch  thi'ough  which  the 
food  must  pass  in  going  from  the  small  to  the  large 
intestine,  was  always  packed  with  putrefying  feces.  ^^ 
They  decided  that  the  mechanical  difficulty  which 
the  animals  have  in  the  removal  of  feces  of  an  un- 
favorable character  from  this  part  of  the  digestive 
tract  was  in  some  way  related  with  the  development 
of  the  disease.  That  this  assumption  was  correct, 
was  sho^^^l  by  the  fact  that  the  administration  of 
hquid  petrolatum,  a  ^'mineral"  product  to  which  no 
food  value  can  possibly  be  attributed,  served  to  re- 
lieve a  certain  number  of  animals  after  they  were 
near  death  from  the  disease,  while  confined  strictly 
to  the  diet  of  oats  and  milk  which  caused  them  to 
develop  scurv^y.  The  ex|3lanation  which  they  offered 
was  that  the  Uciuid  petrolatum  served  to  improve 
the  physical  properties  of  the  contents  of  the  packed 
cecum,  and  thus  enable  the  animals  to  rid  themselves 
of  this  mass  which  was  undergoing  putrefactive  de- 
composition. 

Further  experiments  showed  that  when  the  ani- 
mals were  fed  an  oat  atid  railk  diet,  to  which  was 
added  suitable  doses  of  phenolphthalein,  a  ca- 
thartic, they  could  \\^thstand  the  diet  for  long 
periods  ^\dthout  developing  scurvy.     This,   accord- 


98      THE  NEWER  KNOWLEDGE  OF  NUTRITION 

ing  to  McCoJlum  and  Pitz,  was  due  to  the  addi- 
tional secretion  of  water  into  the  digestive  tract, 
brought  about  by  the  cathartic,  and  resulted  in 
softening  the  feces  so  that  they  were  more  easily 
eliminated  from  the  cecum. 

It  has  long  been  known  that  orange  juice  is  a  very 
efficient  protective  agent  against  scurvy,  both  in  man 
and  the  guinea  pig.  In  fact  it  was  because  of  the 
spectacular  relief  of  the  disease  by  the  administration 
of  orange  juice  or  of  fresh  vegetables,  that  Funk 
was  led  to  the  beUef  that  scurvy  is,  like  beri-beri, 
due  to  the  lack  of  some  specific  chemical  substance 
from  the  food  supply.  McCollum  and  Pitz  further 
tested  their  theory  by  preparing  an  artificial  orange 
juice,  in  which  every  constituent  was  kno^vn,  and 
the  administration  of  this  to  guinea  pigs  which  were 
confined  to  a  diet  of  oats  and  milk,  on  which  food 
supply  they  almost  invariably  develop  the  disease. 
The  '^  artificial  orange  juice  "consisted  only  of  cit- 
ric acid,  cane  sugar  and  inorganic  salts,  in  about  the 
proportions  in  which  these  occur  in  the  edible  portion 
of  the  orange.  It  was  demonstrated  that  this  mix- 
ture exerted  a  decidedly  protective  action  when  added 
to  the  oat  and  milk  diet,  and  prevented  the  develop- 
ment of  scurvy  over  a  long  period. 

Jackson  and  Moore  suggested  that  scurvy  is  a 
bacterial  disease,  and  they  have  secured  experimental 
evidence  which  strongly  supports  that  view.  They 
found  in  the  hemorrhagic  joints  a  diploccocus,  which 
may  have  a  causal  relationship  to  the  disease.    They 


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''DEFICIENCY"   DISEASES  99 

were  able  to  induce  mild  symptoms  of  scuny  by  the 
injection  of  bacterial  cidtui-es  into  animals  which 
were  fed  upon  a  diet  which  regulai-ly  maintains  the 
gmnea  pig  in  a  state  of  health.  AlcCollum  and  Pitz 
hold  the  view  that  there  may  be  an  invasion  of  the 
tissues  by  organisms  as  the  result  of  injuiy  to  the 
cecal  wall,  when  the  animals  are  debihcated.  The 
cecum  is  injuied  by  long  contact  wiih.  the  irritating 
products  formed  by  putrefactive  bacteria  acting  on 
the  protein  substances  contained  in  the  cecum  when 
it  becomes  packed  \yith.  feces  of  such  a  character 
that  they  cannot  be  ehminated.  They  suggested  the 
alternative  hypothesis  .that  there  may  be  formed 
tln^ough  bacterial  activity,  substances  which  are 
toxic,  and  have  such  pharmacological  properties  as 
cause  injur}'  to  the  walls  of  the  capillaries  of  those 
areas  in  which  hemorrhage  is  observed  in  scur\y. 
There  are  several  problems  still  to  be  solved  in  con- 
nection with  the  cause  of  scur\y,  but  it  seems  to  be 
satisfactorily  dem.onsti'ated  that  it  is  not  a  ''de- 
ficiency" disease  in  the  sense  in  which  are  beri-beri 
and  the  type  of  xerophthalmia  of  dietary  orgin.  There 
is,  according  to  ^IcCollum  and  his  co-workers,  no 
protective  substance  against  this  disease.  Diets  of 
faulty  character,  and  especially  bacteriologically  un- 
satisfactor>%  are  responsible  for  its  etiolog>%  and  it 
is  relieved  by  a  satisfactory  diet.  The  peculiar  ana- 
tomical structure  of  the  aUmentary  tract  of  the 
guinea  pig  makes  it  difficult  for  it  to  thrive  unless 
its  diet  contains  a  succulent  vegetable,  which  gives 


100    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

the  feces  favorable  physical   characters  and  which 
makes  them  easy  of  eUmination. 

Hess  ^^  has  recently  described  the  results  of  his 
observations  on  infants  which  were  fed  milk  treated 
in  various  ways,  and  these  are  of  great  significance 
in  throwing  hght  on  the  cause  of  scur\^.  He  points 
out  that  for  a  period  of  two  years  milk  which  had 
been  pasteurized  commercially  at  165°  for  thirty 
minutes  was  employed  in  feeding  the  infants  in  his 
charge.  For  two  subsequent  years  the  dealers  raised 
it  to  only  145°  for  thirty  minutes.  In  his  experience 
the  former  milk  was  more  likely  to  induce  scurvy 
than  the  latter.  Hess  thereafter  secured  raw  cer- 
tified malk  and  pasteurized  it  at  the  institution  for 
thirty  minutes  at  145.°  Infants  fed  this  milk  did  not 
develop  scur\y  in  any  instance,  and  one  which 
showed  symptoms  of  subacute  scur\y  improved  on 
the  home  pasteurized  milk.  How  did  this  milk  differ 
from  the  commercially  pasteurized  milk  which  did 
show  definite  tendency  to  induce  the  disease?  He 
points  out  that  it  differed  mainly  in  the  interval 
which  elapsed  between  the  time  of  the  heating  process 
and  the  time  of  consumption  of  the  milk.  In  New 
York  City,  the  gi'eater  portion  of  the  bottled  milk 
sold  is  of  Grade  B,  most  of  which  is  brought  to  the 
city  for  pasteurization,  which  is  done  soon  after  mid- 
night. ]Much  of  this  is  dehvered  to  the  consum.er 
the  following  morning,  but  a  part  is  allowed  to  stand 
until  the  following  day  before  delivery.  The  city 
milk  of  Grade  A  was  largely  pasteurized  in  the  coun- 


"DEFICIENCY"  DISEASES  101 

try,  and  since  they  stored  the  niilk  for  twenty-four 
hours  after  the  heat  treatment  so  as  to  insure  a  con- 
stant supply  in  case  of  delay  in  the  deliveiy  from  the 
country,  there  was  an  interval  of  forty-eight  hours 
between  the  pasteurization  and  the  deUveiy  of  the 
milk  to  the  consumer.  Hess  reproduced  these  con- 
ditions in  his  institution  by  keeping  milk  pasteurized 
at  145°  for  forty-eight  hours  on  ice.  Of  eight  in- 
fants w^hich  were  fed  the  milk  so  treated,  two  showed 
scorbutic  symptoms,  which  were  relieved  by  giving 
them  orange  juice.  Two  out  of  another  eight  which 
were  fed  milk  which  was  kept  on  ice  forty-eight 
hours  after  the  heat  treatment  showed  signs  of 
scurfy.  In  other  cases  scur\y  was  observed  in 
infants  fed  certified  milk  which  had  not  been  pas- 
teiu-ized,  when  the  latter  had  been  kept  on  the  ice 
forty-eight  hours  before  feeding.  Ageing  is,  therefore, 
effective  in  causing  changes  in  both  raw  and  pasteur- 
ized milk,  so  that  the  danger  of  the  development 
of  scur\y  in  infants  to  wliich  it  is  fed  is  increased. 

Boiled  milk  has  been  extensively  fed  to  infants  in 
various  parts  of  the  world  and  in  the  experience  of 
some  observers  does  not  induce  scur\y.  The  expe- 
rience of  Hess  further  supports  the  view  that  boiled 
roilk  is  less  liable  to  induce  scurfy  than  is  milk  which 
has  been  pasteurized  at  165°  or  at  a  lower  temper- 
ature. jNIilk  which  has  been  pasteurized  at  165°  is 
more  hable  to  induce  scur\y  than  either  boiled  milk, 
or  milk  which  has  been  pasteurized  at  lower  temper- 
atures, as  140-145°  for  thirty  miautes.     The  most 


102    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

satisfactory  explanation  for  these  results  seems  to  be 
found  in  the  bacteriological  condition  of  the  milks 
treated  in  the  various  ways  described.  Heating  milk 
at  165°  kills  nearly  all  the  lactic  acid  forming  bacteria 
which  normally  cause  the  souring  of  milk.  Heating 
for  thirty  minutes  at  140°  to  145°  leaves  some  of  the 
organisms  capable  of  developmeat,  and  milk  so  pas- 
teurized will  sour.  In  the  absence  of  the  acid  formers 
there  develop  during  the  interval  between  heating 
and  consumption  the  spore-forming  organisms  which 
are  not  killed  by  pasteurization.  These  will,  in  time, 
cause  the  putrefactive  decomposition  of  the  milk. 
Any  heat  treatment  which  kills  all  the  acid  formers 
leaves  the  milk  in  a  suitable  condition  for  the  devel- 
opment of  the  pernicious  fonns,  and  old  milk  so 
treated  may  be  a  menace  to  the  health  of  infants, 
and  unfit  for  consmiiption  by  adults.  Boihng  tends 
to  destroy  all  the  organisms  in  milk  and  will  do  so 
if  sufficiently  prolonged.  Such  milk  may  be  more 
suitable  for  food  than  that  which  has  been  so  treated 
as  to  prevent  souring  and  yet  be  in  a  condition  to 
permit  the  growth  of  putrefactive  forms  of  bacteria. 
These  results  strongly  support  the  view  that  there 
is  a  bacteriological  factor  involved  in  the  causation 
of  scur\y,  and  en.phasizes  the  importance  of  securing 
clean  milk,  and  of  ha\dng  it  so  handled  as  to  insure 
its  deUvery  in  a  good  bacteriological  condition. 
Milk  should  not  be  kept  in  the  home  without  efficient 
refrigeration,  and  should  be  consum.ed  before  it 
becomes  stale.     Pasteurization  seems,  in  itself,  to 


"DEFICIENCY"  DISEASES  103 

have  little  influence  in  lowering  the  food  value  of 
milk.  The  staleness  is  the  great  element  of  danger. 
Pasteurization  is  desirable  as  a  safeguard  against 
such  diseases  as  typhoid  fever,  tuberculosis,  scarlet 
fever  and  such  organisms  as  cause  epidemics  of  sore 
throat.  It  does  not  render  milk  permanently  harm- 
less. The  pubUc  should  insist  upon  having  its  milk 
supply  produced  under  hygienic  conditions.  Milk 
should  then  be  cooled  promptly  so  as  to  depress  as 
far  as  possible  the  growth  of  the  organisms  which 
always  find  entrance  through  the  air  and  from  the 
cow  and  the  milker.  It  should  be  carefully  refriger- 
ated, and  promptly  deUvered  and  properly  cared  for 
in  the  home,  and  should  not  be  allowed  to  age  un- 
necessarily before  use.  If  pasteurized,  it  should  pref- 
erably receive  the  lowest  heat  treatment  which  will 
effectively  destroy  the  pathogenic  organisms,  and 
should  be  dehvered  as  promptly  as  possible  there- 
after in  a  suitably  cooled  state.  Stale  milk  is  danger- 
ous, especially  for  use  in  infant  feeding. 

Pellagra. — This  disease  has  been  common  in  parts 
of  Europe  for  centuiies.  It  is  especially  conmion  in 
northern  Italy,  and  has  been  sometimes  referred  to 
as  Alpine  scurv^\  It  is  likewise  known  in  Spain  and 
and  the  south  of  France.  The  disease  was  first  ob- 
served in  America  in  1907,  and  has  been  steadily 
on  the  increase,  especially  in  certain  of  the  Southern 
States.  In  1917  it  was  estimated  that  there  were 
165,000  pellagrins  in  the  United  States. 

Pellagra  is  essentially  a  disease  of  poverty,  al- 


104    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

though  there  are  many  cases  recoided  among  the 
well-to-do.  It  has  been  especially  prevalent  in  the 
country,  in  villages,  and  in  the  poorer  sections  of 
cities,  and  is  obsez'ved  to  occur  most  frequently 
following  periods  of  scarcity  of  food.  In  Europe 
the  disease  was  long  associated  with  the  consumption 
of  spoiled  maize  as  the  chief  article  of  diet,  but  it  is 
now  known  that  the  eating  of  this  grain  has  nothing 
whatever  to  do  with  its  causation.  All  observers 
are  agreed  that  the  diet  is  of  primary  import  in  the 
etiology  of  the  disease,  but  differences  of  opinion 
still  exist  as  to  whether  there  is  hkewise  a  bacteri- 
ological factor  involved. 

The  trouble  begins  with  digestive  disturbances  of 
an  indefinite  character,  followed  by  soreness  of  the 
mouth,  which  renders  eating  difficult,  and  a  per- 
sistent diarrhea  which  saps  the  strength  of  the  pa- 
tient. Skin  eruptions  appear,  and  there  are  formed 
on  parts  of  the  body  dark  crusts  which  sometimes 
suppurate.  In  severe  cases  there  are  pronounced 
nervous  disturbances  preceding  death. 

In  its  early  stages  pellagra  yields  fairly  readily 
to  dietetic  treatment.  Indeed  it  has  been  emphasized 
by  clinicians  that  without  dietary  measures,  there  is 
no  effective  treatment,  and  numerous  cases  are  re- 
corded in  which  the  disease  has  disappeared  promptly 
when  milk,  eggs  and  meats,  string  beans,  together 
with  a  liberal  amount  of  the  leafy  vegetables,  such 
as  cabbage,  collards,  and  lettuce,  were  included  in 
the  diet.^^ 


''DEFICIENCY"   DISEASES  105 

In  the  United  States,  especially,  pellagra  tends  to 
seasonal  occurrence,  most  new  cases  occurring  in  the 
spring,  or  better,  as  Goldberger  has  emphasized, 
at  the  end  of  mnter.  JobUng,  in  his  excellent  survey 
of  pellagra  in  Nashville,  found  that  nearly  all  cases 
had  their  onset  in  the  spring  and  early  summer.  ^^ 
It  frequently  happens  that  sufferers  recover  from 
their  attacks  of  the  disease  during  the  later  summer 
and  fall,  and  suffer  a  relaspe  during  the  following 
spring.  Indeed  the  diet  of  many  of  the  poorer  people 
of  the  South,  during  the  winter,  consists  principally 
of  corn  bread,  pork  and  molasses.  From  what  has 
been  said  in  earlier  chapters,  it  will  be  easily  ap- 
preciated that  such  a  combination  of  food-stuffs  does 
not  constitute  an  adequate  diet,  and  it  is  significant 
that  nearly  all  new  cases  develop  after  a  hundred 
days  or  more  of  confinement  to  such  a  food  supply. 

It  should  be  pointed  out  that  Jobling  and  Peter- 
son emphasize  that  from  their  observations  the 
pellagrins,  and  the  class  from  which  the  new  cases 
develop,  consmne  relatively  much  carbohydrate  and 
relatively  little  protein,  since  they  make  liberal  use 
of  corn  bread,  corn  gi'its,  and  potatoes  and  biscuits 
made  from  bolted  flour,  together  with  molasses, 
There  were  some  who  declared  that  they  had  regu- 
larly eaten  eggs,  butter  milk,  milk  and  meat.  They 
further  point  out  that  in  the  spring,  summer  and 
autumn  months  a  great  deal  of  green  stuff  in  the 
form  of  turnip  tops,  wild  mustard,  green  peas  (seed) 
and  green  onions  are  eaten.    The  green  onions  are 


100    THK  NEWER  KNOWLEDGE  OF  NUTRITION 

eaten  raw,  the  others  cooked.  In  addition,  during 
the  summer  months  much  fruit,  especially  peaches 
and  apples,  are  eaten  since  these  are  usually  cheap. 

In  commenting  upon  the  studies  of  Goldberger, 
JobUng  and  Peterson  point  out  that  the  poorly  nour- 
ished individual  is  prone  to  contract  many  diseases 
and  theu^  observation  that  there  is  a  close  relation- 
ship between  the  sanitaiy  condition  of  the  different 
parts  of  Nashville  and  the  incidence  of  pellagra, 
tends  to  strongly  support  the  view  that  the  disease 
is  associated  with  poor  sewage  disposal.  The  sani- 
tary conditions  in  those  districts  where  pellagra  is 
common  are  of  the  worst  sort,  in  many  instances 
there  being  little  pretense  made  of  doing  anything 
with  the  excreta,  which  during  the  summer  is  usually 
covered  with  flies.  Screening  was  usually  absent 
from  those  houses  where  the  disease  was  found. 
Jobling  and  Peterson  are  essentially  in  accord  with 
the  conclusions  of  the  Thompson-McFadden  Com- 
mission ^^  which  made  a  thorough  investigation  of 
conditions  in  Spartanburg  County,  S.  C,  where 
pellagra  is  a  scourge,  and  arrived  at  the  conclusion 
that  the  disease  is  in  some  way  related  to  a  bacte- 
riological factor,  and  is  probably  distributed  by  an 
insect. 

Golderger  has  accom.pHshed  a  great  work  in  demon- 
strating that  the  diet,  when  properly  constituted, 
causes  the  disappearance  of  pellagra,  and  prevents 
its  recurrence.  His  dietary  studies  have  demon- 
strated beyond  a  reasonable  doubt  that  a  faulty 


"DEFICIENCY"   DISEASES  107 

diet  is  the  most  important  factor  in  causing  the  de- 
velopmxent  of  the  condition.  He  has  sho\^Ti  that 
when  hberal  amounts  of  milk  and  eggs  and  of  meat, 
are  introduced  into  the  diet  of  institutions,  such 
as  insane  asylums  and  orphanages,  in  which  the  dis- 
ease was  previously  common,  they  become  free  from 
it  even  though  new  cases  are  admitted  freely  and 
the  sick  are  mingled  with  the  well.  He  and  his  co- 
workers have  likewise  made  heroic  attempts  to 
transmit  the  disease  to  themselves  by  means  of  the 
administration  of  the  excreta  and  material  from  the 
lesions  of  pellagrins,  but  without  success,  when  the 
experimenters  were  taking  a  satisfactory  diet.-^ 

An  expermient  on  man,  which  was  carried  out  by 
Goldberger,  is  of  special  interest.  A  diet  consisting 
of  dishes  prepared  fi^om  degerminated  corn  meal, 
bolted  wheat  flour,  rice,  starch,  sugar,  pork  fat,  to- 
gether with  sweet  potatoes,  cabbage,  collards,  turnip 
greens  and  coffee,  induced  the  appearance  of  what 
were  regarded  as  the  incipient  signs  of  the  disease  by 
the  end  of  five  and  a  half  months  in  five  of  eleven 
men,  who  volunteered  to  submit  themselves  to  this 
dietar}^  regime.- 

Chittenden  and  Underhill  -^  have  described  ex- 
periments in  which  dogs  were  restricted  to  a  diet  of 
crackers  (wheat  flour),  cooked  (dried)  peas  and 
cottonseed  oil.  After  intervals  vary-ing  from  two  to 
eight  months,  the  animals  developed  the  t>^ical  sore 
mouth,  severe  diarrhea  and  skin  changes  strikingly 
suggestive  of  pellagra  in  man.     They  were  of  the 


108    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

opinion  that  this  diet  caused  these  symptoms  be- 
cause of  the  lack  of  some  substance  or  substances  of 
the  class  designated  as  'Sdtamines"  by  Funk. 

McCollum,  Simmonds  and  Parsons  ^*  demon- 
strated that  the  diet  of  Chittenden  and  Underhill, 
which  consisted  of  bolted  wheat  flour,  peas  and 
cottonseed  oil,  cannot  be  deficient  in  any  other  uni- 
dentified dietary  essential  than  the  fat-soluble  A,  a 
lack  of  which  is  associated  wdth  the  development  of 
the  eye  disease,  xerophthalmia.  Tliis  conclusion  is 
necessary  since  rats  were  shown  to  fail  to  grow  or 
remain  in  a  state  of  health,  on  this  mixture,  and  that 
it  is  rendered  dietetically  sufficiently  com.plete  by 
the  addition  of  three  types  of  purified  food  sub- 
stances, viz.,  mineral  salts,  protein,  and  fat-soluble 
A,  to  induce  growth  at  the  normal  rate.  The  animals 
failed,  however,  to  successfully  rear  young.  The 
first  limiting  factor  is  the  inorganic  content.  Every- 
thing of  an  unknown  chemical  nature  which  the  diet 
must  contain  is  present  in  a  mixture  of  wheat  flour, 
peas  and  cottonseed  oil,  but  there  is  a  relative  short- 
age of  the  fat-soluble  A,  which  is  abunda>nt  in  cer- 
tain fats,  and  is  associated  with  cellular  structures 
generally  in  both  animal  and  vegetable  food-stuffs. 
McCollum,  Simmonds  and  Parsons  pointed  out  that 
although  their  rats  failed  to  mxaintain  satisfactory 
nutrition  on  this  food  mixture,  unless  the  three 
kinds  of  supplements  were  added,  there  was  no 
soreness  of  the  mouth  or  diarrhea,  such  as  was  ob- 
served by  Chittenden  and  Underhill  in  dogs,  and  are 


"DEFICIENCY"  DISEASES  109 

usually  present  in  pellagra  in  man.  The  eyes  became 
swollen  when  the  diet  was  supplemented  only  by 
salts. 

An  inspection  of  the  diets  described  by  Goldberger 
as  common  in  those  institutions  where  pellagi^a  is 
prevalent,  and  the  winter  diets  of  people  in  those 
districts  where  there  is  a  high  incidence  of  the  dis- 
ease m  the  spring  and  summer  months,  shows  that 
these  are  composed  largely  of  seeds  and  seed  prod- 
ucts, and  the  amounts  of  leafy  vegetables,  milk, 
eggs  and  meat,  are  very  small,  or  are  enthely  absent, 
for  vaiying  periods.  McCollum  and  Sinmionds  -^ 
have  pointed  out  that  in  the  exi3erimental  diet  with 
w^hich  Goldberger  reported  having  produced  incipi- 
ent pellagi'a  in  man,  about  ninety-six  per  cent  of  the 
total  solids  of  the  food  supply  w^as  derived  from  seed 
products:  corn  mesl,  \\"heat  flour,  rice,  starch,  sugar, 
molasses  and  from  pork  fat,  and  only  about  four  per 
cent  from  sweet  potatoes  and  the  leafy  vegetables 
together.  Such  a  small  amount  of  the  leaf  does  not 
suffice  to  make  good  the  dietary^  deficiencies  of  the 
seed  products  in  such  a  diet.  These  deficiencies  are 
now  well  understood,  and  it  is  further  known  that 
the  tubers,  such  as  the  potato  and  sweet  potato,  are 
not  so  constituted  as  to  serve  as  '^protective"  foods 
when  taken  together  with  seed  products.  The  diets 
of  those  people  who  suffer  from  pellagra  are,  there- 
fore, deficient  in  three  respects.  They  are  relatively 
low  in  protein  and  their  proteins  are  of  relatively 
poor  biological  value,  because  they  do  not  yield  on 


110    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

digestion,  a  favorable  mixture  of  amino-acids  for  the 
transformation  into  body  tissues.  They  lack  a 
sufficient  amount  of  the  unidentified  dietary  essential 
fat-soluble  A,  and  also  of  certain  mineral  elements. 
The  latter  fault  is  in  most  instances  limited  to  a 
shortage  of  calcium,  sodium  and  chlorine.  Since  it 
is  the  regular  practice  of  man  to  make  additions  of 
sodium  chloride  in  the  form  of  table  salt,  to  his  diet, 
the  mineral  deficiency  in  these  diets  may  be  said  to 
be  limited  to  the  element  calcium.  Any  one  of  these 
faults  alone  is  sufficient  to  induce  malnutrition  when 
either  the  young  or  the  adult  animal  is  restricted  to 
such  diets  as  are  common  in  pellagra  stricken  districts. 
Since,  however,  there  seems  to  be  good  evidence 
that  there  sometimes  occur  cases  of  pellagra  in  in- 
dividuals whose  diets  have  included  a  certain  amount 
of  such  articles  as  AlcCollum  and  his  co-workers 
have  designated  as  PROTECTIVE  FOODS,  viz., 
milk,  eggs  and  the  leafy  vegetables,  the  theory  of 
an  infection  is  supported.  The  prevalence  of  the 
disease  in  badly  sewered  districts  supports  this  view. 
That  there  is  a  bacteriological  factor  involved  in 
pellagra  is  further  supported  in  some  degree  by  the 
fact  that  McCollum,  Sinmionds  and  Parsons  ^^  ob- 
served only  malnutrition  without  diarrhea  or  sore 
mouth  in  rats  fed  diets  which  in  the  experience  of 
Chittenden  and  Underhill  produce  in  dogs  the  gastro- 
intestinal symptoms  seen  in  pellagra  in  man.  The 
sloughing  of  the  mucous  membranes  of  the  mouth, 
and  the  presence  of  ulcers  in  the  intestine  affords 


"DEFICIENCY"  DISEASES  111 

conclusive  evidence  of  an  infection  in  their  dogs. 
McCollmn  and  co-workers  found  no  unhealthy  ap- 
pearance in  the  mucosa  of  the  digestive  tract,  even 
when  theii'  rats  were  moribund  as  the  result  of  being 
fed  only  wheat  flour,  peas  and  cottonseed  oil.  It 
seems  probable  that  the  difference  in  this  respect  in 
the  two  species  may  well  be  attributed  to  a  chance 
infection  in  the  one  case  which  did  not  occur  in  the 
other.  These  observations  are  in  harmony  with  the 
fact  that  not  everyone  who  takes  the  poor  diets  de- 
scribed develops  the  disease.  It  seems  logical  in  the 
light  of  all  the  data  available,  to  conclude  that  poor 
nutrition  predisposes  to  infection,  and  that  there  is 
an  infectious  agent  involved  in  the  production  of 
pellagra.  There  can  be  no  reasonable  doubt  that 
the  possibility  that  pellagi^a  is  a  ^^ deficiency"  dis- 
ease, in  the  sense  in  which  Funk  employed  this  term, 
is  definitely  answered  in  the  negative  by  the  ex- 
perimental work  of  McCoUum  and  his  co-workers. 

Rickets. — There  can  be  no  doubt  that  rickets  is  a 
nutritional  disease,  but  its  relation  to  the  diet  is  not 
clear.  It  is  characterized  especially  by  an  alteration 
in  the  growth  of  the  bones.  These  become  enlarged 
at  the  extremities  and  so  soft  that  they  bend  under 
the  stress  of  muscular  contz^action  and  under  the 
weight  of  the  body.  It  is  a  disease  of  the  fii'st  two 
years  of  life,  and  is  especially  prevalent  in  children 
in  whose  diet  milk  is  replaced  too  largely  by  cereals 
and  other  vegetable  foods,  not  saited  to  the  delicate 
digestive  tract  of  the  young  child.     Predisposing 


112    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

factors  in  many  cases  are  undoubtedly  tuberculosis 
and  syphilis.  The  symptoms  develop  gradually. 
Restlessness  and  perspiration  at  night,  great  sen- 
sitiveness of  the  limbs,  that  even  a  light  touch  is 
extremely  painful,  are  characteristic  signs  of  the 
disease.  There  are  gastro-intestinal  disturbances, 
especially  colic  and  distension  of  the  intestine  with 
gas,  so  that  the  abdomen  protrudes.  The  bones 
become  thickened,  and  nodules  develop  at  the  junc- 
tures of  the  ribs  with  the  costal  cartilages,  forming 
the  characteristic  ^^ beaded"  ribs.  There  is  defective 
ossification  of  the  skull;  the  teeth  appear  later  than 
normal  and  in  unusual  order.  Various  deformities 
of  the  head,  spine,  chest  and  limbs  result  as  the  child 
develops.  Recovery  with  deformity  is  of  frequent 
occurrence. 

There  must,  at  the  present  time,  be  an  element  of 
speculation  in  any  discussion  of  the  relation  of  diet 
to  rickets.  The  well-known  deficiencies  from  the 
dietary  standpoint  of  the  cereal  grains  and  the  other 
storage  organs,  together  with  the  injury  to  the  in- 
testine, which  is  nearly  always  present,  as  shown  by 
the  distended  abdomen,  and  the  occurrence  of 
rickets  only  in  early  life,  and  so  frequently  in  associa- 
tion with  infectious  disease,  all  make  it  unnecessary 
to  invoke  the  aid  of  any  hypothetical  ^'vitamine," 
to  a  lack  of  which  the  disease  may  be  attributed. 

Hess  -^  has  recently  described  the  results  of  his 
dietary  studies  among  the  negro  women  of  the 
Columbus  Hill  district  in  New  York,  whose  children 


'^DEFICIENCY"  DISEASES  113 

almost  all  suffer  from  rickets.  It  is  significant  that 
these  women  are  attempting,  hke  the  very  poor  in 
many  cities,  to  live  on  a  diet  derived  from  the  en- 
dosperm of  wheat,  maize  and  rice,  bolted  flour, 
degerminated  cormneal,  pohshed  rice,  together  with 
tubers  and  meats.  It  will  be  evident  from  the  data 
furnished  by  the  application  of  the  biological  method 
for  the  analysis  of  food-stuffs,  which  McCollum  and 
his  co-workers  have  perfected,  and  which  was  de- 
scribed in  Chapters  I  to  III,  that  there  are  no  com- 
binations of  those  food-stuffs  whose  functions  are 
those  of  storage  organs,  which  will  constitute  a  satis- 
factory diet  for  gi'owth.  Muscle  tissue  does  not  tend, 
except  in  respect  to  the  protein  factor,  to  correct  the 
dietary  faults  of  such  mixtures.  The  regular  con- 
sumption of  such  diets  will  in  the  course  of  a  few 
months  cause  a  distinct  lowering  of  the  vitality  of 
an  adult  and  will  cause  even  greater  injury  to  the 
young  child.  In  a  later  chapter  it  mil  be  showm  that 
the  milk  of  mothers  taking  such  diets  does  not 
satisfactorily  nourish  the  young. 

Wliat  has  said  been  above  regarding  the  special 
dietaiy  properties  of  the  different  food-stuffs  which 
go  to  make  up  the  diet  of  civilized  man,  and  the 
dietaiy  habits  of  those  classes  of  people  who  suffer 
from  the  diseases  which  have  come  to  be  recognized 
as  being  due  to  faulty  diet,  make  it  easy  to  see  that 
there  has  become  fixed  in  the  minds  of  students  of 
nutrition  and  of  the  reading  public,  an  altogether 
exti'avagant  idea  regarding  the  importance  of  the 


114    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

substances  to  which  Funk  gave  the  name  ^'vita- 
muies."  Of  the  diseases  which  Funk  considered  due 
to  lack  of  unidentified  substances  of  this  nature, 
viz.,  bcri-beri,  scurvy,  pellagra  and  rickets,  but  one, 
beri-beri,  has  been  shown  to  be  due  to  this  cause. 
In  the  course  of  the  analysis  by  McCollum  and  Davis, 
of  the  problem  of  what  chemical  complexes  are  nec- 
essary to  constitute  the  simplest  diet  which  will 
serve  to  support  growth  in  the  young,  and  maintain 
physiological  well-being  in  the  adult,  a  second  dietary 
^'deficiency"  disease  in  the  same  sense  as  beri-beri, 
was  discovered,  and  shown  to  have  occurred  sporad- 
ically in  man.  This  is  the  t^^e  of  xerophthalmia 
which  results  from  a  deficiency  of  the  dietaiy  essen- 
tial of  unknowTi  chemical  nature,  fat-soluble  A. 
Beri-beri  is  due  to  the  lack  of  the  second  unknown 
dietary  essential  w^ater-soluble  B.  Pellagra,  scurvy 
and  rickets  do  not  belong  in  the  same  category  with 
beri-beri,  and  there  do  not  exist  "curative"  sub- 
stances of  unknown  nature  for  these  diseases.  The 
individual  is  predisposed  to  the  development  of  these 
syndromes  by  faulty  diet,  but  the  faults  have  been 
shown  by  the  biological  method  for  the  analysis  of 
the  individual  food-stuffs  or  their  mixtures,  to  reside 
in  maladjustments,  and  unsatisfactoiy  quantitative 
relationships  among  the  now  w^ell-recognized  con- 
stituents of  the  normal  diet.  They  are  to  be  sought 
in  the  quality  and  quantity  of  the  protein,  the  char- 
acter and  amiount  of  the  inorganic  constituents,  the 
physical  properties  of  the  residues  which  are  left 


"DEFICIEXCY"  DISEASES  115 

after  digestion,  and  form  the  feces  from  which  the 
intestine  must  rid  itself.  It  seems  probable  that 
the  only  unidentified  substance  which  is  physiolog- 
ically indispensable,  which  is  not  sufficiently  abun- 
dant in  the  diets  employed  by  the  people  of  the 
United  States  and  Europe  where  there  are  used  in- 
sufficient amounts  of  milk,  butter,  cream,  eggs  and 
the  leafy  vegetables,  is  the  fat-soluble  A,  but  occa- 
sionally diets  may  be  met  with  which  contain  too 
Kttle  of  the  water-soluble  B.  Sufficient  knowledge  is 
now  available  to  make  it  possible  to  select  such  foods 
as  will  mutually  make  good  each  other's  deficiencies, 
and  to  combine  them  in  such  proportions  as  will 
insure  the  disappearance  of  all  the  diseases  of  man 
which  are  brought  on  by  faulty  diets.  The  same 
knowledge  will,  in  the  future,  make  possible  an 
efficient  utilization  of  feeding-stuffs  for  anim^al  pro- 
duction, which  will  be  of  inestimable  economic 
value  to  mankind. 


CH.\PTER  VI 

THE  NURSING  MOTHER  AS  A  FACTOR  OF  SAFETY  IN  THE 
NUTRITION    OF   THE    SUCKLING 

Anyone  who  reflects  upon  the  relation  of  the 
mother  to  her  young  during  the  suckhng  period, 
must  marv^el  at  the  fact  that  during  early  hfe  the 
young  mammal  cannot  thrive  on  the  diet  of  the 
adult.  It  must  have  milk  for  a  shorter  or  longer 
period  after  birth.  This  the  lactating  animal  is  able 
to  form  from  her  food  thi'ough  the  agency  of  the 
mammary  gland.  The  period  of  dependency  varies 
greatly  in  different  species.  Among  mammals, 
with  which  the  author  is  famiUar,  the  young  guinea 
pig  is  born  in  the  most  highly  developed  state.  The 
newborn  ca\y  is  capable  of  eating  grass  or  succulent 
vegetables  during  the  first  or  second  day  of  post- 
natal life.  The  young  rat  may  be  safely  weaned  at 
the  age  of  twenty-five  days,  provided  a  highly  satis- 
factory diet  of  the  t^^De  which  sufficies  for  the  adult 
is  then  supplied.  The  young  pig  (swdne)  becomes 
able  to  eat  fahly  hberally  of  the  normal  adult  diet 
at  the  age  of  six  or  eight  weeks,  w^hereas  the  human 
uifant  must  live  largely  on  a  milk  diet  during  the 
first  year  of  hfe  and  should  have  a  liberal  allowance 
of  milk  and  of  eggs  during  the  entire  growing  period. 

116 


3     O   -Tt     O   773 


THE  NURSING  MOTHER  117 

Even  eggs  will  not  entirely  replace  milk  during  any 
part  of  this  period.  It  is  of  great  importance  that 
we  should  understand  the  relationship  between  the 
character  of  the  diet  of  the  lactating  female,  and  the 
quahty  of  the  milk  which  she  is  able  to  produce. 
Our  knowledge  of  this  subject  is  still  very  incomplete, 
but  experimental  studies  on  animals  have  recently 
thrown  hght  on  certain  very  importaDt  phases  of 
this  problem. 

In  order  to  gain  information  on  the  relation  be- 
tween the  character  of  the  diet  of  the  mother  and 
the  value  of  the  milk  which  she  produces,  McCollum 
and  Simmonds  ^  carried  out  a  series  of  experunents 
on  lactating  rats,  whose  diets  were  faulty  in  known 
ways,  and  observed  the  effect  on  the  growth  of  the 
young  which  these  mothers  nursed.  The  mothers 
were  fed  a  highly  satisfactory  diet  until  they  had 
completed  their  term  of  jDregnancy.  As  soon  as  the 
young  were  born,  the  litter  was  in  all  cases  reduced 
to  four,  in  order  that  the  nutritive  undertaldng  of 
the  mother  should  in  no  case  be  burdensomxe.  The 
mother  was  at  once  restricted  to  a  diet  which  would 
not  induce  any  growth  whatever  in  a  young  rat  after 
separation  from  the  mother  at  weaning  time.  The 
diets  of  the  mothers  in  the  various  experunents  were 
faulty  in  respect  to  each  of  the  factors  which  are 
necessary  for  the  formation  of  a  satisfactory^  diet, 
but  the  number  of  characters  in  which  a  single  diet 
was  faulty  varied  from  oue  to  three. 

In  one  case  the  mother  was  fed  upon  a  diet  of 


118    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

purified  protein,  carbohydrate  (dextrinized  starch), 
a  suitably  constituted  inorganic  salt  mixture,  and 
an  alcoholic  extract  of  wheat  germ  to  furnish  the 
unidentified  dietary  essential,  water-soluble  B.  This 
diet  contained  everything  necessary  for  the  nutiition 
of  a  young  rat  during  growth,  except  the  fat-soluble 
A.  The  problem  w^as  to  find  whether  the  mother 
could,  through  the  agency  of  the  mammary  gland, 
form  the  missing  substance,  fat-soluble  A.  Expe- 
rience has  shoT\Ti  that  the  young  animal  after  the 
weaning  age,  cannot  produce  it  de  novo,  for  its  own 
preservation  from  any  of  the  other  constituents  of 
its  food.  The  results  of  the  experiment  indicated 
that  the  quantity  of  the  fat-soluble  A  in  the  milk 
produced  from  such  a  diet  is  below  the  amount 
necessary  for  the  promotion  of  the  maximum  rate 
of  growth  in  the  young.  It  has  been  shown  by 
Osborne  and  Mendel,-  that  the  body  fats  of  beef 
cattle  contain  a  small  amount  of  the  fat-soluble  A. 
It  seems  certain  that  the  body  fats  of  an  animal 
which  has  been  fed  for  some  time  on  a  diet  rich  in 
this  substance,  will  serve  as  a  reserve  supply  of  this 
dietary  essential,  which  the  mother  can  secrete  into 
the  milk.  In  other  experiments.  Chart  15,  definite 
evidence  is  presented  that  this  substance  is  not 
abundant  in  the  milk  unless  it  is  present  in  the  diet 
of  the  mother.  The  presence  of  some  fat-soluble  A 
in  the  tissues  of  the  mother  makes  it  especially  diffi- 
cult to  obtain  milk  which  is  entkely  free  from  this 
substance. 


THE  NURSING  MOTHER  119 

Through  similar  experiments  with  diets  which 
contained  the  fatr-soluble  A,  but  not  the  water- 
soluble  B,  evidence  was  secured  that  for  a  time  the 
mother  is  able  to  secure  this  dietary  factor  from  her 
reserve  supply,  but  none  of  the  growth  curves  in- 
dicated that  the  substance  is  present  in  the  milk 
in  adequate  amount  when  the  diet  of  the  mother 
lacks  it.  It  seems  certain  that  neither  of'  these 
substances  is  present  in  abundance  in  the  milk  of 
the  mother,  unless  it  is  furnished  in  her  food. 

Evidence  confirmatory  of  this  view  is  found  in 
the  studies  of  Andrews  ^  on  infantile  beri-beri.  It 
is  well  known  that  the  faulty  diet  of  rice  and  fish, 
which  fui-nishes  the  principal  food  of  many  of  the 
poorer  classes  of  the  Orient,  does  not  prevent  the 
onset  of  beri-beri,  and  infants  who  nurse  mothers 
who  are  suffering  from  the  disease,  likewise  develop 
beri-beri.  Andrews  induced  several  Filipino  women 
whose  infants  had  just  died  of  beri-beri,  to  nurse 
young  pups,  and  noted  that  in  all  cases  the  lat- 
ter failed  to  grow,  became  edematous,  and  lost 
the  use  of  their  hind  legs.  Paralysis  of  the  posterior 
extremities  is  one  of  the  symptoms  of  the  disease  in 
man.  It  is  evident  that  in  the  milk  of  these  mothers 
there  w^as  a  shortage  of  the  water-soluble  B,  for  it 
is  a  shortage  of  this  substance  which  causes  the 
development  of  this  sjTidrome. 

It  has  been  pointed  out  that  young  animals  do 
not  grow  when  confined  to  a  single  seed  or  mixture  of 
seeds  of  plants,  for  the  reason  that  these  are  all 


120    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

lacking  in  sufficient  amounts  of  the  inorganic  el- 
ements, calcium,  sodium  and  chlorine,  and  are  too 
poor  in  the  fat-soluble  A  to  support  normal  nutrition. 
The  quaUty  of  their  proteins  is  likewise  too  poor 
to  make  them  very  satisfactory  for  the  support  of 
growth.  McCollum  and  Simmonds  have  studied 
the  extent  to  which  the  mother  is  able  to  produce 
milk  of  satisfactory  character  for  the  promotion  of 
growth  in  the  young,  when  confined  to  a  single  seed  as 
the  sole  source  of  nutriment.  Charts  15  and  16  show 
the  effects  of  such  diets  on  the  growth  of  the  young. 
The  curves  of  rat  211  and  of  her  fitter  of  four 
young  (Chart  15)  illustrate  the  remarkable  growth 
which  a  mother  rat  is  able  to  induce  in  her  young 
when  her  diet  is  highly  satisfactory,  and  while 
doing  so,  she  is  able  to  increase  her  own  weight  very 
appreciably.  In  marked  contrast  to  this  '' normal '^ 
accomplishment  stands  the  failure  of  rat  738  to  in- 
duce more  than  one-third  the  normal  rate  of  growth 
in  her  young  when  restricted  to  rolled  oats  as  her 
sole  food  supply.  The  drop  in  the  curve  of  the 
young  at  the  40th  day  was  the  result  of  the  death 
of  the  young  at  brief  intervals.  The  mother  lost 
weight  regularly,  showing  that  she  was  sacrificing 
her  own  tissues  for  the  preservation  of  her  young. 
Rolled  oats,  like  the  other  seeds,  require  improve- 
ment in  respect  to  three  dietary  factors  before  it 
becomes  a  complete  food,  and  on  such  a  faulty  diet 
the  mother  produces  milk  which  is  not  satisfactory 
for  the  promotion  of  growth  in  her  offspring. 


THE  NURSING  MOTHER  121 

Rat  843,  whose  diet  consisted  of  rolled  oats  sup- 
plemented with  fat-soluble  A  (as  butter  fat)  induced 
growth  in  her  young  at  a  somewhat  greater  rate  than 
she  could  have  done,  had  she  eaten  oats  alone,  and 
was  able  to  keep  them  alive  for  a  longer  period. 
The  first  one  died  on  the  57th  day  and  the  others 
followed  in  rapid  succession.  This  mother  lost  con- 
siderable weight  up  to  the  time  that  the  3^0  ung  began 
to  eat  of  the  oat  and  butter  fat  diet.  Young  rats, 
after  removal  from  the  mother,  cannot  gi'ow  at  aU 
on  this  diet. 

Rat  899,  was  fed  a  diet  of  rolled  oats  to  which  was 
added  such  an  inorganic  salt  mixture  as  made  good 
the  mineral  deficiencies  of  the  oat  kernel.  Her  diet 
was  still  deficient  in  fat-soluble  A,  and  to  some  extent 
in  the  quality  of  its  proteins.  With  this  food  her 
milk  was  of  distinctly  better  quality  than  that  which 
can  be  produced  on  a  diet  of  oats  alone,  or  on  oats 
supplemented  with  fat-soluble  A,  or  on  oats  supple- 
mented vdth  purified  protein  (rat  948) .  From  these 
results  it  is  apparent  that  the  first  limiting  factor 
of  the  oat  kernel  for  milk  production  in  the  lactating 
animal  is  the  same  as  in  the  young  for  growth,  viz., 
the  inorganic  content  of  the  food  supply. 

The  importance  of  having  the  inorganic  content 
of  the  diet  properly  constituted  is  shown  especially 
well  in  the  perfonnance  of  the  mothers  983  and 
1978.  The  former  was  fed  rolled  oats  supplemented 
with  both  fat-soluble  A,  in  the  form  of  butter  fat, 
and  pmified  protein  in  the  form  of  casein  of  milk. 


122    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

Even  with  these  two  additions  she  was  able  to  induce 
less  than  half  normal  growth  in  her  young  and  they 
began  to  die  at  the  age  of  45  days,  and  all  succumbed 
in  rapid  succession.  Rat  1978,  on  the  other  hand, 
whose  diet  consisted  of  rolled  oats  supplemented 
with  a  suitable  salt  mixture  and  butter  fat,  was  able 
to  induce  growth  in. her  young  at  about  two-thirds 
the  normal  rate.  The  improvement  of  the  milk 
by  the  inclusion  of  fat-soluble  A  in  the  diet  is  very 
apparent,  since  the  young  did  not  die  during  the 
period  of  sixty  days  covered  by  the  experiment,  and 
supports  the  view  that  this  substance  cannot  be 
synthesized  by  the  mother. 

Rat  1019,  whose  diefc  consisted  of  rolled  oats 
supplemented  with  purified  protein  and  a  suitable 
salt  mixture,  shows  that  the  mother  is  able  to  induce 
nearly  the  optimum  rate  of  growth  in  her  young  dur- 
ing a  period  of  thirty  days,  although  her  diet  was  very 
poor  in  the  factor  fat-soluble  A.  It  should  be  borne 
in  mind  that  the  seeds,  because  they  contain  a  small 
proportion  of  cellular  structures  in  addition  to  their 
reserve  food  package  in  the  endosperm,  contain  a 
small  but  inadequate  amount  of  the  fat-soluble  A. 
The  mother  is  able,  when  the  diet  of  oats  is  corrected 
with  respect  to  two  factors,  protein  and  salts,  to 
concentrate  in  the  milk  the  small  content  of  the  fat- 
soluble  A  which  her  diet  supplies.  She  is  probably 
also  able  to  draw  in  some  degree  upon  her  small 
store  of  this  substance  which  is  deposited  in  her  body 
fats,  and  supply  the  young  with  enough  of  it  to 


THE  NURSING  MOTHER  123 

enable  them  to  reach  a  state  of  relative  independence, 
which  in  a  wild  state  would  enable  them  to  go  in 
search  of  food  for  themselves.  There  is  abundant 
experimental  proof  that  when  the  protein  and  in- 
organic content  of  the  food  are  of  liighly  satisfactory 
character,  animals  can  subsist  for  a  long  period  on  a 
supply  of  fat-soluble  A  too  small  to  prevent  the  onset 
of  xerophthalmia  in  diets  of  lower  biological  value. 

These  records  of  nursing  mothers  and  their  young 
make  it  apparent  that  the  former  is  limited  in  a 
general  way  in  the  utilization  of  food  for  milk  pro- 
duction, in  the  same  manner  as  in  the  growing  young 
in  the  utilization  of  food  for  the  construction  of  new 
body  tissues.  She  is,  however,  a  factor  of  safety  for 
her  young  in  no  small  degree.  It  should  be  remem- 
bered that  a  young  rat  cannot  grow  at  all  when, 
after  the  weaning  age,  it  is  limited  to  the  oat  kernel, 
or  to  the  oat  kernel  supplemented  with  either  salts, 
protein  or  fat-soluble  A  alone,  or  on  a  diet  of  oats 
supplemented  with  both  protein  and  fat-soluble  A. 
In  order  that  it  may  grow  even  very  slowly  it  is 
essential  that  both  a  suitable  salt  mixture  and  fat- 
soluble  A  shall  be  added  to  the  oat  kernel.  It  can- 
not grow  normally  unless  the  protein  factor  is  like- 
wise improved.  In  the  records  of  the  mothers  and 
young  shown  in  Chart  15,  the  young  continued  to 
grow  in  certain  instances  after  the  twenty-fifth  day, 
the  age  at  which  they  may  be  safely  weaned  when 
their  milk  supply  has  been  of  normal  composition. 
This  fact  is  conclusive  evidence  that  even  after  the 


124    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

young  become  able  to  eat  of  the  diet  on  which  the 
mother  had  produced  the  milk  on  which  they  were 
able  to  grow — Si  diet  on  which  they  would  be  unable 
to  grow  at  all  without  some  corrections  and  improve- 
ments— they  were  still  receiving  a  supplementary 
milk  supply  from  the  mother.  This  served  to  correct 
in  some  measure  the  faulty  diet  of  oats  plus  an  in- 
complete supplementary  addition.  It  seems  certain 
that  milk  production  must  have  been  very  con- 
siderable in  amount,  to  thus  enhance  the  diet  of 
four  young  whose  weight  collectively  was  about  half 
that  of  the  miother  herself. 

The  inorganic  content  of  all  the  seeds  is  the  first 
hmiting  factor  in  preventing  growth  in  young  ani- 
mals, and  in  determining  the  quality  of  the  milk  which 
can  be  produced  from  them.  The  young  animal 
cannot  grow  at  all  on  seeds  unless  one  of  the  factors 
corrected  includes  certain  salt  additions,  yet  the 
mother  is  able  to  produce  milk  without  any  such 
additions,  which  is  capable  of  inducing  a  limited 
amount  of  growth  in  the  3^oung.  It  is  apparent  that 
one  of  her  most  important  relations  to  her  helpless 
offspring  is  her  capacity  to  supply  it  with  a  better 
inorganic  food  supply  than  she  herself  secures  in  her 
food,  when  the  latter  is  of  poor  quality. 

The  growth  curves  of  the  young  of  mothers  whose 
diets  consisted  of  the  oat  kernel  without  and  with 
purified  food  additions,  illustrate  likewise  very  well 
the  results  which  are  observed  when  similar  ex- 
periments are  conducted  with  the  wheat  or  maize 


THE  NURSING  MOTHER  125 

kernel.  They  emphasize  the  fact  that  for  milk  pro- 
duction as  for  growth,  the  seeds  of  plants  may  be  re- 
garded as  closely  similar  in  their  dietary  properties. 
It  is  therefore,  rendered  highly  probable  that  the 
same  analogy  runs  through  the  series  of  food-stuffs 
in  their  value  for  the  production  of  milk  of  normal 
character.  We  are  not  to  expect,  therefore,  that  a 
diet  consisting  of  even  a  complex  mixture  of  seeds, 
tubers  and  roots,  will  produce  milk  of  highly  satis- 
factory character,  and  without  undue  strain  on  the 
mother.  It  lias  been  emphasized  that  even  this  Ust 
of  foods  of  the  class  whose  functions  are  those  of  stor- 
age organs,  do  not  suffice  even  when  combined  with 
meat,  to  induce  satisfactory  growth  in  the  young. 
It  follows  as  a  logical  conclusion,  that  a  lactating 
mother  will  not  be  able  to  produce  milk  of  a  very  sat- 
isfactory character  when  she  is  restricted  to  such 
food-stuffs.  It  should  be  reiterated  that  there  are 
two  classes  of  food-stuffs  which  are  so  constituted  as 
to  correct  the  deficiencies  of  seeds,  tubers,  roots  and 
meat.  These  are  milk  and  the  leaves  of  plants  and 
they  should  be  used  very  liberally  in  the  diet.  Eggs 
are  in  some  degree  to  be  regarded  as  comparable  to 
these,  but  eggs  have  not  the  favorable  mineral  con- 
tent of  the  leaves  and  of  milk,  and  this  is  one  of  the 
most  important  factors  in  which  the  storage  organs 
of  plants  need  supplementing. 

The  question  will  arise  in  the  minds  of  many,  as 
to  whether  the  inability  of  the  young  to  grow  on  the 
milk  produced  by  mothers  which  were  Uving  upon 


126    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

an  inadequate  diet,  was  not  the  result  of  the  failure 
of  the  mothers  to  produce  enough  niilk  rather  than 
milk  of  abnormal  composition.  It  has  not  been 
found  possible  to  secure  complete  information  as  to 
the  actual  amount  of  milk  which  these  rats  secreted, 
but  we  have  analogous  data  from  domestic  animals, 
which  support  the  view  that  milk  secretion  remains 
fairly  constant  in  the  lactating  animal  even  under 
very  unfavorable  conditions  of  nutrition. 

Babcock  ^  has  described  experiments  in  which  he 
deprived  cows  of  common  salt  during  lactation, 
other  than  that  which  they  secured  in  their  regular 
ration,  which  was  of  a  type  suitable  for  the  dairy 
cow.  The  keen  appetite  of  the  herbivora  for  salt  is 
a  matter  of  common  knowledge.  Deer  which  are 
very  shy  will  risk  any  danger  to  secure  salt  at  their 
accustomed  licks  or  from  salt  springs.  The  periods 
of  salt  deprivation  varied  from  two  to  fifteen  months, 
and  some  of  the  animals  actually  died,  and  others 
were  saved  from  death  by  the  administration  of  salt. 
In  no  instance  was  there  a  notable  decrease  in  the 
yield  of  milk  by  these  cows  up  to  a  short  time  be- 
fore they  began  to  fail  rapidly.  Indeed  the  fat  con- 
tent of  the  milk  of  the  cows  receiving  an  inadequate 
salt  supply  was  slightly  higher  than  in  the  milk  of 
the  control  group. 

Eccles  and  Pahner  ^  have  conducted  a  very  thor- 
ough experimental  study  of  the  influence  of  under- 
feeding of  cows  on  milk  production,  and  have  studied 
its  composition  in  cows  whose  rations  were  of  suitable 


THE  NURSING  MOTHER  127 

composition,  but  inadequate  in  amount.  These 
results  show  that  cows  were  able,  during  the  early 
part  of  the  lactation  period,  to  maintain  the  milk 
flow  undiminished  for  forty  days,  when  receiving 
but  75  per  cent  enough  food  to  meet  her  require- 
ments. Under  such  conditions  of  nutrition  there 
was  no  pronounced  change  in  the  composition  of  the 
milk.  During  the  latter  part  of  the  lactation  period 
there  was  some  falling  off  in  milk  production  as  the 
result  of  under-feeding. 

Ducaisne  ^  in  1870,  noted  that  during  the  siege  of 
Paris,  young  and  vigorous  women  were  able  to  pro- 
duce enough  milk  to  maintain  their  infants,  and  in 
some  cases  to  increase  their  weight  when  they  were 
partially  fasting.  These  observations,  as  well  as 
those  of  Andrews  on  women  w^hose  infants  had  died 
of  beri-beri,^  all  support  the  view  that  under  con- 
ditions of  faulty  nutrition,  it  is  the  quality  of  the 
milk  rather  than  the  quantity  which  early  suffers 
impairment.  Dr.  IManuel  Roxas,  of  the  College  of 
Agriculture  of  the  Philippine  Islands,  has  informed 
the  author  in  a  private  conxmunication,  that  the  in- 
fants' death  rate  among  the  natives  is  much  higher 
in  the  breast-fed  than  among  the  bottle-fed  children. 

The  occurrence  of  infantile  beri-beri,  rather  than 
of  death  from  starvation,  further  serves  to  demon- 
strate that  it  is  milk  of  poor  quality,  rather  than 
lack  of  sufficient  amount  of  milk  which  is  responsible 
for  the  high  infant  mortality  in  those  parts  of  the 
world  where  the  poorer  classes  live  too  largely  on 


128    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

food-stuffs  derived  from  products  whose  biological 
functions  are  those  of  storage  organs,  and  meat. 

The  statement  which  one  sees  reiterated  so  fre- 
quently, that  breast  feeding  of  infants  is  superior  to 
the  best  system  of  artificial  feeding,  need3  to  be 
qualified  to  some  extent.  There  are,  without  ques- 
tion, in  many  parts  of  the  world,  large  groups  of 
people  whose  diets  are  of  such  a  character  that  the 
quaUty  of  the  milk  produced  by  the  lactating  mother 
is  not  such  as  to  make  it  a  satisfactory  food  for  their 
infants.  It  should  be  thoroughly  appreciated  that 
the  human  mother  should  have  in  her  diet  a  liberal 
amount  of  milk  in  order  to  safeguard  the  health  and 
well-being  of  her  infant,  and  of  leafy  vegetables, 
which  serve  the  two-fold  function  of  a  protective 
food  and  of  greatly  aiding  intestinal  elimination. 
That  some  mothers  can  induce  a  fair  amount  of 
growth  in  their  infants  while  taking  a  faulty  diet, 
cannot  be  denied,  but  that  both  mother  and  child 
suffer  impairment  as  the  result  is  beyond  question. 
It  is  not  enough  that  the  diet  shall  furnish  enough 
calories  and  enough  protein,  and  shall  afford  variety 
and  palatabihty.  The  peculiar  dietary  properties 
of  the  food-stuffs  which  enter  into  the  diet  are  of 
paramount  importance,  and  must  be  taken  into  con- 
sideration. 

Attention  should  again  be  directed  to  the  observa- 
tions of  Hess^  that  the  diet  of  the  negro  women  of 
the  Columbus  Hill  district  in  New  York,  whose  diets 
are  derived  almost  exclusively  from  seed  products, 


THE  NURSING  MOTHER  129 

tubers  and  meats,  fail  to  nourish  their  infants  satis- 
factorily as  sho\\Ti  by  the  almost  universal  prevalence 
of  rickets  among  the  latter.  It  is  difficult  for  man 
to  correct  the  dietary  deficiencies  of  these  products 
by  the  use  of  the  leaves  of  plants  as  his  sole  protective 
food,  because  of  the  limited  capacity  of  his  digestive 
tract.  ^lilk  in  liheral  amounts  should  always  be 
included  m  the  diet  of  the  lactating  mother. 


CHAPTER  VII 

PRACTICAL  CONSIDERATIONS  WHICH  SHOULD  GUIDE  IN 
THE    PLANNING    OF   THE    DIET 

In  the  preceding  chapters  there  were  presented 
data,  which  have  been  obtained  by  biological 
methods,  concerning  the  special  dietary  properties 
of  the  several  classes  of  natural  food-stuffs,  which 
enter  into  the  diets  of  man  and  animals.  It  is  evident 
from  the  experiments  described  that  a  diet  may  fur- 
nish an  abundance  of  protein  and  energy,  and  may 
be  easy  of  digestion,  and  may  furnish  a  wide  variety 
and  include  several  seeds  or  products  derived  from 
these,  together  with  tubers,  roots  and  meats,  and 
may  be  highly  acceptable  to  the  hum.an  palate  and 
yet  fail  utterly  to  support  satisfactory  nutrition. 
In  the  light  of  such  facts,  it  becomes  apparent  that 
a  chemical  analysis  of  a  food-stuff  throws  no  hght 
whatever  upon  certain  aspects  of  its  dietary  prop- 
erties. It  is  only  by  biological  methods  that  we  can 
arrive  at  principles  which  can  serve  as  a  safe  guide  as 
to  the  method  of  procedure  by  means  of  which  safe 
diets  can  be  planned.  In  the  present  chapter  will  be 
discussed  a  number  of  questions  which  always  arise 
in  the  minds  of  those  who  wish  to  apply  the  new 
knowledge  to  the  planning  of  a  suitable  dietary 
regime. 

130 


THE  PLANNING  OF  THE  DIET  131 

It  should  be  understood  that  it  is  neither  necessary 
or  desirable  that  we  should  abandon  the  customary 
classification  of  food-stuffs  on  the  basis  of  chemical 
composition.  We  must  have  a  language  of  nutrition, 
and  consider  foods  on  the  basis  of  their  protein, 
carboh^'drate,  fat,  water  and  mineral  content,  as  we 
have  always  done.  We  should  be  familiar  with  the 
quota  of  energ}'  available  from  the  different  t^-pes  of 
foods.  We  must,  however,  take  into  consideration 
certain  facts  wliich  have  not  hitherto  been  considered, 
and  concerning  which  a  chemical  analysis  gives  no 
information. 

One  of  the  outstanding  results  of  modern  research 
in  nutrition  is  the  great  difference  in  the  biological 
values  of  the  proteins  from  different  sources.  In  a 
general  way  this  is  appreciated  by  aU  well  informed 
teachers  of  the  present  day,  but  many  are  still  in 
need  of  clearer  distinctions  regarding  what  data  m 
the  hterature  are  capable  of  direct  appUcation  to 
practical  nutrition,  and  what  are  of  such  a  nature 
that  they  cannot  be  so  apphed.  No  lack  of  apprecia- 
tion is  intended  of  data  of  the  latter  t^^e,  for  they 
may  have,  and  indeed  frequently  have  a  value  of 
the  first  importance  to  the  investigator  in  this  field. 
As  an  example  may  be  cited  the  laborious  studies 
through  which  the  amino-acids  became  kno\\Ti,  and 
the  data  yielded  by  such  method  of  analysis  of  the 
proteins  as  those  of  Fischer  and  of  Van  Slyke.  Im- 
portant as  are  these  results  in  making  possible  fur- 
ther progress,  they  are  not  of  such  a  character  that 


132    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

they  can  be  applied,  as  has  been  frequently  at- 
tempted, in  making  deductions  concerning  com- 
parative food  values.  It  is,  however,  through  such 
studies  that  we  have  arrived  at  a  satisfactory  working 
h^^Dothesis  concerning  the  nature  of  the  proteins, 
and  have  become  able  to  appreciate  why  the  proteins 
have  different  values  in  nutrition.  Our  analytical 
methods  do  not  make  possible  an  approximately 
quantitative  determination  of  more  than  a  third  of 
the  total  number  of  the  digestion  products  of  the 
proteins.  An  attempt  to  utiUze  the  figures  for  the 
yield  of  this  or  that  amino-acid  by  one  or  another  of 
the  proteins,  as  evidence  of  the  comparative  values 
of  the  proteins  themselves,  or  of  the  food-stuffs  from 
which  they  are  deiived,  will  lead  to  entirely  fallacious 
deduction. 

Such  data  as  are  tabulated  in  the  literature  for  the 
yields  of  the  different  amino-acids,  m^ake  the  pea 
and  bean  proteins  appear  superior  to  those  of  the 
cereal  grains.  AlcCollum  and  Simmonds  have  re- 
ported a  long  series  of  ex^Deriments  with  diets  so 
planned  that  they  were  adequate  in  all  respects, 
and  the  protein  content  was  derived  entirely  from  a 
single  seed.  The  amount  of  protein  in  the  diet  was 
varied  so  as  to  find  in  one  series  what  was  the  lowest 
per  cent  of  protein  in  the  food  nuixture  which  would 
just  m.aintain  a  grown  rat  over  a  period  of  several 
months  without  loss  of  body  weight,  and  in  another 
series,  the  minimum  amount  of  protein  was  deter- 
mined which  would  induce  in  the  young,  half  normal 


THE  PLANNING  OF  THE  DIET  133 

and  full  normal  rate  of  growth  respectively.  The 
data  regarding  the  values  of  several  of  the  more  im- 
portant seed  proteins  for  maintenance  are  of  great 
interest.  Rats  can  be  maintained  in  body  weight 
on  suitably  constituted  diets  containing  4.5  per  cent 
of  oat  protein,  or  of  millet  seed  protein;  on  6  per  cent 
of  maize,  rice  or  wheat  proteins ;  on  about  8  per  cent 
of  flax-seed  protein,  whereas  it  requires  about  11  to 
12  per  cent  of  the  proteins  of  the  pea  or  the  bean  to 
accomplish  the  same  result. 

Chemical  analysis  shows  the  proteins  of  the  pea 
and  bean  to  contain  all  the  kno\vTi  ammo-acids, 
and  none  of  these  are  present  in  excessive  or  in  min- 
imal quantities,  whereas  the  wheat  and  m^aize  pro- 
teins yield  excessive  amounts  of  one  of  them  in  par- 
ticular. Glutamic  acid,  one  of  the  digestion  products 
of  proteins,  is  present  in  the  proteins  of  the  muscle 
tissues  of  animals,  in  the  case  of  no  less  than  half  a 
dozen  species,  to  the  extent  of  twelve  to  fourteen 
per  cent.  The  same  acid  is  present  in  the  two  prin- 
cipal proteins  of  the  wheat  kernel  to  the  extent 
of  nearly  40  per  cent,  and  in  the  principal  protein 
of  the  maize  kernel  to  the  extent  of  about  25  per 
cent.  These  proteins  show  other  differences  in  com- 
position which  led  to  the  behef  that  they  were  of 
relatively  low  biological  value  for  growth,  before 
they  were  studied  satisfactorily  by  appropriately 
planned  feeding  experiments,  all  of  which  have  con- 
firmed this  view.  The  observation  that  the  split 
pea  and  na\^  bean  proteins  are  of  much  less  value  in 


134    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

nutrition  came  therefore  as  a  distinct  surprise,  since 
these  results  were  not  what  were  expected,  in  view 
of  the  tabulated  yields  of  the  several  amino-acids 
shown  by  the  most  careful  chemical  analysis.  The 
data  obtained  by  properly  planned  feeding  experi- 
ments are  highly  reliable,  those  from  the  chemical 
analysis  very  unsafe,  from  which  to  draw  deductions. 
It  should  be  understood  that  these  values  for  the 
proteins  of  the  seeds  apply  only  to  the  proteins  of 
the  single  seed  when  fed  as  the  sole  source  of  protein. 
When  fed  in  mixtures  of  two  or  more  proteins  having 
individually  low  values  for  the  support  of  growth,  they 
may  mutually  make  good  each  other's  amino-acid 
deficiencies,  and  form  a  mixture  which  is  better  than 
either  constituent  when  fed  singly.  Since  this  was 
to.be  expected,  McCollum,  Simmonds  and  Parsons 
have  made  many  feeding  trials  with  simple  com- 
binations of  two  seeds,  such  as  two  cereal  grains,  one 
cereal  and  one  legume  seed  (pea,  bean) ;  one  seed  and 
one  leaf,  etc.,  as  the  sole  source  of  protein  in  the  diet, 
and  have  sought  to  find  which  are  the  m.ost  fortunate 
combinations  of  the  most  important  food-stuffs  for 
the  production  of  protein  mixtures  of  high  biolog- 
ical values  for  the  support  of  growth.  These  trials 
have  shown  that,  while  such  mixtures  of  proteins  are 
superior  to  the  individual  foods  fed  separately  as 
som"ces  of  protein,  it  has  not  been  found  possible  to 
obtain  protein  mixtures  from  vegetable  sources  which 
even  approximate  the  value  of  milk  proteins,  for  the 
support  of  maintenance  or  growth. 


THE  PLANNING  OF  THE  DIET  135 

The  nitrogen-containiiig  compounds  of  the  potato 
have  been  lauded  by  several  investigators  as  being  of 
extraordinary  value  as  a  source  of  protein.  AIc- 
Collum,  Sinimonds  and  Parsons  have  studied  the 
proteins  of  the  potato,  both  for  maintenance  and 
growi-h,  in  experiments  m  which  this  tuber  served  as 
the  sole  source  of  protein,  and  all  its  dietary  defi- 
ciencies were  made  good  by  suitable  additions  of 
purified  food  substances.  These  all  indicate  that 
when  fed  as  the  sole  source  of  protein,  the  nitrogen 
compounds  of  the  potato  have  a  distinctly  lower 
value  than  have  the  proteins  of  the  cereal  grains, 
oat,  wheat,  rice  and  maize. 

Enough  has  been  said  regarding  the  great  dif- 
ferences in  the  values  of  the  proteins  from  different 
sources,  to  make  it  clear  that  it  is  impossible  to  say 
how  much  protein  the  diet  should  contain  \\dthout 
having  a  knowledge  of  the  values  of  the  proteins 
which  the  diet  contains.  Chemical  methods  of 
analysis  are  not  yet  sufficiently  perfected  to  throw 
any  appreciable  light  on  the  values  of  the  mixtures 
of  proteins  which  occur  in  our  natural  foods. 

The  great  attractiveness  of  the  ^S'itamine"  hy- 
pothesis of  Funk,  as  an  explanation  for  all  the  states 
of  malnutrition  which  are  referable  to  faulty  diet, 
has  led,  m  recent  years,  to  much  discussion  of  the 
question  of  the  possible  deterioration  of  foods  during 
cooking,  canning  and  dr^^ing.  The  demonstration 
by  ]\IcCollum  and  his  co-workers  that  there  are  but 
two  unidentified  dietary  essentials,  and  but  two  diet- 


136    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

ary  ''deficiency"  diseases,  due  respectively  to  a 
shortage  of  one  or  the  other  of  these  substances,  fat- 
soluble  A  and  water-soluble  B,  and  that  there  are  no 
''growth  determinants"  unnecessary  for  the  mainte- 
nance of  health  in  the  adult,  does  not  minimize  the 
importance  of  this  subject.  The  work  of  a  number 
of  investigators  has  shown  that  the  water-soluble  B, 
the  protective  substance  against  beri-beri,  is  readily 
destroyed  when  an  excess  of  even  such  weak  alkalies 
as  soda  are  added  to  the  food,  suggests  that  this 
substance  may  be  of  an  unstable  character. 

Osborne  and  Mendel  ^  have  shown  that  butter 
fat  may  have  a  blast  of  steam  passed  through  it  for 
two  hours  and  still  retain  its  peculiar  growth-pro- 
moting properties,  due  to  the  presence  of  the  fat- 
soluble  A.  This  observation  is  in  harmony  with 
those  of  McCollum  and  Davis,  that  heating  butter 
fat  at  the  temperature  of  boiling  water  does  not 
affect  its  peculiar  dietary  value.  It  is  apparent, 
therefore,  that  any  conditions  to  which  milk  fats  are 
liable  to  be  subjected  during  the  cooking  of  foods 
will  not  greatly  alter  its  value  as  a  source  of  the  fat- 
soluble  A.  McCollum  and  Simmonds  have  recently 
(unpublished  data)  tested  a  sample  of  butter  fat 
prepared  from  evaporated  milk,  furnished  to  them 
by  Dr.  Lucius  P.  Brown  of  New  York  City,  and  have 
found  it  very  effective  in  relieving  the  xerophthalmia 
in  rats,  brought  on  by  the  lack  of  the  fat-soluble  A 
in  their  diets.  It  appears,  therefore,  that  there  is  no 
great  deterioration  in  the  quality  of  milk  fats  brought 


THE  PLANNING  OF  THE  DIET  137 

about  by  the  processes  of  removal  of  water  in  the 
preparation  of  condensed  or  evaporated  milks.  They 
have  likewise  shown,  as  have  also  Osborne  and  Men- 
del, that  dried  milks  still  contain  the  fat-soluble  A 
in  abundance.  There  can  be  no  serious  objection  to 
the  use  of  dried  or  canned  milks  on  the  basis  of  their 
value  with  respect  to  this  dietary  essential. 

The  situation  is  likewise  quite  clear  with  respect 
to  the  ordinary  dried  foods.  Leaves  such  as  celery 
tops  and  those  of  the  immature  alfalfa  plant,  when 
dried  in  the  ordinaiy  way,  are  still  good  sources 
of  the  fat-soluble  A.  The  alfalfa  leaves  were  dried 
in  the  sun  and  the  celery  tops  by  artificial  heat  in  a 
current  of  air  after  a  preliminary  treatment  with 
steam. 

iMcCollum  and  Davis  -  have  pointed  out  that 
wheat  germ  can  be  moistened  and  heated  in  an  auto- 
clave at  fifteen  pounds  pressure  for  an  hour  or  more 
without  any  extensive  destruction  of  the  water- 
soluble  B,  and  McCollum,  Simmonds  and  Pitz  ^  have 
subjected  soaked  navy  beans  to  similar  treatment 
without  causing  any  great  deterioration  with  respect 
to  this  dietary  factor.  This  treatment  is  comparable 
to  that  to  which  fruits  and  vegetables  are  subjected 
when  processed  in  canning,  and  shows  that  the  wide- 
spread belief  that  canned  foods  have  lost  these  diet- 
ary essentials  is,  at  least,  generally  without  foun- 
dation. The  cooking  of  beans  or  greens  with  the 
addition  of  soda,  which  is  a  common  practice,  may 
cause  the  destiniction  of  one  or  both  of  the  unidentified 


138    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

dietary  essentials.  At  least  in  the  case  of  the  water- 
soluble  B,  this  will  probably  be  true  if  sufficient 
soda  is  added  to  render  the  food  alkaline.  The  use 
of  soda  in  biscuit  making  will,  according  to  Voegtlin, 
and  Sullivan  ^  cause  the  destruction  of  the  water- 
soluble  B,  for  they  found  that  corn  meal  cooked  with 
soda  was  no  longer  effective  in  causing  the  ^^cure'* 
of  beri-beri  in  pigeons. 

In  this  connection  it  should  be  borne  in  mind  that 
our  ordinary  foods  all  contain  several  times  the 
amount  of  the  water-soluble  B  which  is  necessary 
for  the  maintenance  of  growth  and  health  in  animals. 
There  seems  to  be  no  valid  reason  why,  if  it  is  neces- 
sary for  culinary  purposes,  to  use  soda  in  the  cook- 
ing of  a  few  foods,  the  practice  should  be  discontinued. 
If  the  diet  is  so  planned  as  to  furnish  a  suitable  quota 
of  milk,  and  of  cereals  and  other  foods  which  are  not 
so  treated  as  to  destroy  the  water-soluble  B  there  is 
no  danger  of  a  shortage  of  this  substance  in  the  diet. 
It  is  now  well  demonstrated  that  with  the  diets  employed 
in  Europe  and  America  there  is  no  such  thing  as  a 
"vitamine^^  problem  other  than  that  of  securing  an 
adequate  amount  of  the  substance  fat-soluble  A.  Seeds 
and  their  products,  tubers,  roots  and  meats  in  the 
amount  in  which  they  are  ordinarily  consumed,  do 
not  furnish  enough  of  this  substance  for  the  mainte- 
nance of  an  optimum  state  of  well-being.  Diets  com- 
posed of  these  substances  exclusively,  may,  when 
their  other  deficiencies  are  corrected,  contain  enough 
of  the  fat-soluble  A  to  induce  fairly  good  growth  to 


THE  PLANNING  OF  THE  DIET  139 

nearly  the  full  adult  size,  and  may  long  prevent  the 
development  of  xerophthalmia.  They  do  not  supply 
enough  of  it  to  support  maximum  vigor  over  a  long 
period,  and  fall  short  of  the  amount  necessary  under 
the  special  conditions  involved  in  pregnancy  and 
lactation. 

There  is  a  wdde-spread  belief  that  wheat  is  superior 
to  the  other  cereals  as  a  food.  There  is  no  experi- 
mental e\ddence  that  this  is  tiue.  Rye,  barley,  oats 
and  maize  resemble  wheat  very  closely  in  their  diet- 
ary properties,  and  it  is  safe  to  say  that  these  can 
entirely  replace  wheat  in  the  diet  of  children,  adults 
and  invalids  wdthout  the  least  detriment  to  health. 
Those  who  have  become  accustomed  to  the  use  of 
wheat  bread,  are  attached  to  it  principally  because 
of  habit.  Dietary  habits  becom.e  very  firmly  fixed 
and  are  hard  to  break  away  from.  Millions  in  the 
Orient  are  greatly  attached  to  rice  as  a  food,  and 
feel  that  they  cannot  hve  without  it,  whereas,  we  in 
America  cannot  bring  ourselves  to  eat  liberally  of  it 
in  the  simple  and  unappetizing  form  in  which  it  is 
entirely  acceptable  in  the  Oriental.  The  Italian 
feels  that  no  diet  is  satisfactory  unless  it  contains 
macaroni.  Garlic  and  other  flavors  which  appeal  to 
the  appetite  of  certain  peoples  are  disliked  by  others. 
These  prejudices  and  many  others  are  not  expressions 
of  physiological  need,  but  are  purely  demands  for 
something  to  which  we  have  become  accustomed. 
When  properly  cooked,  cornmeal,  oats  and  other 
cereals  have  never  been  shown  to  produce  digestive 


140    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

disturbances.  Reports  that  the  people  of  Belgium, 
when  restricted  to  the  scanty  fare  which  could  be 
furnished  them  after  the  occupation  of  their  territory 
by  Germany,  suffered  from  digestive  disturbances 
from  eating  corn  bread,  are  not  to  be  taken  as  evi- 
dence that  the  corn  products  were  in  themselves  re- 
sponsible for  the  trouble.  They  were  the  sequel  of 
an  inadequate  diet  which  impaired  the  vitality. 
Experiments  have  been  described,  showing  that 
bolted  wheat  flour  is  inferior  to  whole  wheat. ^  If 
two  pigeons  are  fed  whole  wheat  and  bolted  flour  re- 
spectively, while  a  third  is  allowed  to  fast,  the  first 
will  remain  in  a  state  of  apparent  health  for  several 
weeks,  the  second  will  lose  weight  and  die  earlier  than 
the  fasting  one.  This  does  not  mean  that  bolted  flour 
is  poisonous,  but  only  that  it  is  a  more  incomplete 
food  than  whole  wheat.  The  pigeon  which  is  fed 
whole  wheat  will  succumb  in  the  course  of  tim.e,  for 
whole  w^heat  is  not  a  complete  food.  The  pigeon 
which  fasts  gradually  wastes  away,  but  slowly,  be- 
cause all  the  tissues  decrease  in  volume  and  its  physi- 
ological processes  slow  down.  The  bird  w^hich  is  fed 
the  bolted  flour  dies  earlier  than  the  fasted  one,  be- 
cause the  burden  of  digesting  and  metabolizing  a 
liberal  intake  of  food  requires  that  his  metabolic 
processes  go  on  at  a  rapid  rate.  When  this  demand 
is  made  upon  it  and  its  diet  is  so  incomplete  that 
there  can  be  no  repair  of  its  wasted  tissues,  it  wears 
out  the  more  quickly.  Such  demonstrations  do  not 
constitute  an  argument  against  the  use  of  wheat  flour 


THE  PLANNING  OF  THE  DIET  141 

as  a  food.  In  so  far  as  the  latter  supplies  protein, 
energy  and  inorganic  salts,  it  is  a  good  food.  AATiat 
we  should  realize  is  that  none  of  our  vegetable  foods 
or  the  meats  are  complete  and  ideal  foods.  Some  are 
more  deficient  than  others,  and  their  deficiencies  are 
not  all  ahke.  Satisfactoiy  nutrition  is  to  be  attained 
only  through  the  employment  of  the  right  combi- 
nations of  foods,  and  in  such  proportions  as  \^dll  in- 
sure that  the  resulting  diet  wdll  be  properly  con- 
stituted. We  should  accept  our  natural  foods  for 
what  they  are,  and  make  proper  use  of  them,  rather 
than  condemn  this  or  that  one  because  it  is  lacking 
in  some  respect. 

It  is  fallacious  reasoning  to  attempt  to  compare 
the  money  value  of  certain  foods  with  certain  others. 
We  may  safely  compare  the  cost  of  the  cereal  grains 
or  the  legumes  mth  each  other,  or  with  the  tubers 
such  as  the  potato  or  the  sweet  potato,  or  with  the 
root  foods.  It  is  not  possible  to  compare  the  cost  of 
any  of  these  with  milk  or  the  leafy  vegetables  such 
as  cabbage,  cauliflower,  Swiss  chard,  collards, 
Brussel  sprouts,  onions,  lettuce,  celery  tops,  spinach, 
turnip  tops  and  other  leaves  employed  as  greens. 
]\Iilk  and  the  leafy  vegetables  are  to  be  regarded  as 
protective  foods.  In  some  degree  eggs  are  to  be  con- 
sidered in  the  same  class.  ]\Iilk  and  the  leafy  vege- 
tables should  be  taken  in  liberal  amounts.  The 
leaves  should  not  be  regarded  as  foods  of  low  value 
because  their  content  of  protein,  fat  and  carbohy- 
drate is  low,  and  the  content  of  water  high.    "\ATien 


142    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

compared  on  the  basis  of  chemical  composition  they 
appear  inferior  to  seeds,  but  they  have  a  pecuHar 
value  in  their  high  content  of  fat-soluble  A  and  of 
mineral  elements,  which  makes  them  stand  in  a 
class  by  themselves  among  the  vegetable  food-stuffs. 

No  thorough  studies  of  the  dietary  properties  of 
fruits  have  yet  been  made,  but  from  their  known 
chemical  composition  and  biological  functions  as 
storage  organs,  their  proper  place  in  the  diet  can  be 
predicted.  They  are  good  sources  of  mineral  salts 
and  of  energy-yielding  foods,  the  sugars.  They  are 
highly  palatable  and  exert  a  favorable  influence  on 
the  excretory  processes  of  the  kidneys  and  the  in- 
testine. Their  liberal  use  in  the  diet  should  be  en- 
couraged. 

Owing  to  the  present  shortage  of  certain  food- 
stuffs, there  has  been  a  tendency  to  consider  the  in- 
troduction of  certain  new  products  hitherto  not 
generally  employed  in  a  large  way  as  human  foods, 
and  to  extend  their  use  by  extolling  their  virtues. 
Conspicuous  among  these  are  the  peanut  press  cake, 
which  remains  after  the  oil  is  extracted  by  pressure, 
the  soy  bean  and  cottonseed  flour.  The  latter  prod- 
uct represents  a  portion  of  the  cottonseed  which  is 
prepared  by  first  removing  the  oil,  and  afterward 
grinding  and  bolting  to  obtain  a  product  free  from 
hulls  and  fiber.  These  movements  directed  toward 
the  utilization  of  all  our  food  resources  are  laudable, 
but  the  information  which  is  disseminated  con- 
cerning these  products  by  their  enthusiastic  pro- 


THE  PLANNING  OF  THE  DIET  143 

moters  is  not  in  all  cases  accurate  and  sufficiently 
complete  to  serve  as  a  safe  guide  to  the  user.  They 
are  extolled  in  the  time- honored  fashion  as  foods 
rich  in  protein  and  energy,  but  their  exact  place  in 
the  dietary  is  not  sufficiently  emphasized. 

There  can  be  no  doubt  that  the  peanut  is  a  whole- 
some food,  and  can  be  used  to  advantage  in  the  diet 
of  man  in  moderate  amounts.  It  is  likewise  a  good 
source  of  protein  of  fairly  good  quahty.  The  same 
can  be  said  of  the  soy  bean.  The  proteins  of  neither 
of  these  have  extraordinary^  values.  That  there  are 
no  proteins  of  extraordinary  values  in  the  seeds  of 
plants  yet  studied,  is  apparent  from  a  critical  and 
unprejudiced  inspection  of  all  of  the  extensive  ex- 
permiental  data  available.  The  point  to  be  em- 
phasized in  this  comiection,  is  that  these  are  seed  prod- 
ucts, and  have  in  a  general  way  the  peculiar  dietary 
properties  common  to  seeds.  Their  place  in  the  diet 
is  therefore  clear.  They  may  be  employed  in  moder- 
ate amounts  along  with  other  seeds  and  seed  prod- 
ucts, provided  that  they  are  supplemented  with 
sufficient  amounts  of  the  protective  foods,  milk  and 
the  leafy  vegetables. 

With  respect  to  cottonseed  products  the  case  is 
som.ewhat  different.  The  cottonseed  has  long  been 
known  to  contain  something  toxic  to  animals,  and  ex- 
perience has  taught  that  cottonseed  meal,  a  product 
containing  the  hulls,  cannot  be  fed  hberally  to  animals 
without  disastrous  results.  Withers  and  Carruth*^ 
have  conducted  extensive  investigations  regarding 


144    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

the  nature  of  the  toxic  constituent,  and  have  iso- 
lated it  as  a  substance  to  wliich  the  name  gossypol 
has  been  given.  It  is  destroyed  by  oxidation,  and 
by  appropriate  heat  treatment,  and  some  cotton- 
seed products  are  much  less  poisonous  than  others, 
because  of  the  special  treatment  which  they  have 
received.  The  author  has  fed  cottonseed  flour  to  a 
large  number  of  animals,  and  is  convinced  that  it 
should  not  be  employed  in  the  human  dietary  in  very 
Uberal  amounts.  If  the  diet  is  appropriately  con- 
stituted with  respect  to  its  content  of  the  protective 
foods,  cottonseed  flour  which  has  been  thoroughly 
cooked,  will,  when  used  in  moderation,  be  found  to  be 
a  useful  food-stuff.  The  data  available  emphasize  the 
need  for  further  careful  studies  to  show  how  much 
heat  treatment  is  necessary  to  render  cottonseed 
flour  harmless.  Such  knowledge,  when  available, 
will  m.ake  possible  the  standardization  of  commercial 
products,  and  will  make  possible  the  utihzation  of 
this  vast  food  resource. 

The  paramount  importance  of  maintaining  and 
of  increasing  the  production  of  milk  makes  it  neces- 
sary to  utilize  a  large  amount  of  protein-rich  foods  in 
the  dairy  industry.  The  wisest  plan  is  to  extend  the 
use  of  peanut,  soy  bean  and  cottonseed  products  for 
milk  production.  The  cow  produces  much  of  her 
milk  from  coarse  feeds,  not  suitable  for  human  con- 
sumption, but  requires  liberal  protein-rich  supple- 
ments in  addition.  Greater  emphasis  should  be  laid 
upon  the  wisdom  of  a  more  liberal  purchase  of  milk 


THE  PLANNING  OF  THE  DIET  145 

by  the  public.  This  would  insure  the  best  utiliza- 
tion of  these  protein-rich  products  which  have  not 
as  yet  m  many  quarters  found  extensive  use  as  hu- 
man foods.  Experimental  data  seems  to  have  es- 
tablished that  the  proteins  of  the  peanut  and  the  soy 
bean  are  of  better  quaUty  than  those  of  the  pea  or 
the  na\^  bean.  From  the  author's  studies  of  the  soy 
bean  it  appears  that  its  proteins  have  about  the 
same  quality  as  those  of  the  cereal  grains,  but  it  con- 
tains thi'ee  times  as  much  protein  as  the  latter.  Its 
content  of  fat-soluble  A  is  such  that  a  mixture  of 
soy  bean  and  starch  wliich  has  the  same  protein  con- 
tent as  the  wheat  kernel,  probably  has  about  the 
same  dietary  properties  as  has  wheat  with  respect  to 
these  two  dietaiy  factors.  There  is  no  reason  why 
the  peanut  and  soy  bean  should  not  be  employed  to 
a  greater  extent  as  human  foods,  but  it  should  be 
kept  in  mind  that  good  use  is  already  being  made  of 
these  products  in  the  feeding  of  dairy  cows,  and  that 
if  the}"  are  T\ithdra\\^i  from  this  application  for  use 
as  human  foods  directly,  it  will  not  be  easy  to  find 
something  to  take  their  place  in  the  dairy  mdustry. 
Several  writers  have  pointed  out  that  these  seeds 
contain  the  fat-soluble  A,  and  have  exhibited  growth 
curves  which  indicate  that  animals  have  taken  one  of 
these  seeds  properly  supplemented  so  as  to  correct 
its  deficiencies,  and  have  been  able  to  grow  to  ap- 
proximately the  full  adult  size  without  the  addition 
of  more  of  this  dietary  essential.  The  reader  is  left 
with  the  impression  that  the  peanut,  soy  bean  and 


146    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

cottonseed  may  serve  as  an  adequate  source  of  fat- 
soluble  A.  This  impression  is  an  unfortunate  one, 
for  it  is  certain  that  even  with  diets  which  are  com- 
posed largely  of  these  seeds,  the  content  of  this  sub- 
stance is  below  the  optimum,  and  in  the  amounts  in 
which  they  are  hkely  to  enter  into  the  human  diet, 
they  will  never  serve  as  a  substitute  for  the  pro- 
tective foods.  In  the  enthusiastic  apphcation  of  the 
biological  method  for  the  analysis  of  food-stuffs,  by 
those  wdth  Uttle  experience,  after  its  description  by 
McCollum  and  Davis  in  1915,^  hasty  conclusions 
have  been  drawTi  in  a  number  of  instances.  Mc- 
Collum and  Simmonds  have  emphasized  the  necessity 
of  observing  over  long  periods,  such  animals  as  are 
able  to  grow  at  about  the  normal  rate  and  produce 
a  few  young  and  rear  them,  when  confined  to  ex- 
perimental diets.  In  many  instances  it  is  found  that 
the  interval  between  litters  is  too  long,  or  the  mor- 
tahty  of  the  young  abnormally  high,  the  time  neces- 
sary to  bring  the  young  to  the  weaning  stage  too 
long  and  the  signs  of  old  age  appear  too  early,  in 
animals  which  during  the  early  part  of  the  reproduc- 
tive period  appeared  to  be  nearly  normal  in  all  re- 
spects. They  have  reached  the  conclusion  that  it  is 
necessary  to  observe  the  behavior  of  the  second 
generation  when  confined  to  the  diet  of  the  parent 
before  drawing  final  Conclusions  concerning  the 
quality  of  a  diet.  In  many  instances  lack  of  vitaHty 
is  first  observed  in  the  inability  of  the  offspring  to 
develop  normally  on  a  diet  which  would,  in  the  early 


THE  PLANNING  OF  THE  DIET  147 

life  of  the  parent,  have  been  considered  entirely  sat- 
isfactory. WTien  observations  are  extended  in  this 
way,  it  becomes  apparent  that  lung  infections  very 
frequently  terminate  the  Uves  of  the  animals,  whose 
diets  are  faulty  in  some  degree,  but  not  so  faulty  as  to 
make  their  effects  strikingly  apparent. 

From  many  questions  asked  by  the  public  the  au- 
thor has  gained  the  con\iction  that  faulty  deductions 
have  been  drawTi  by  others  from  experimental 
studies,  which  would  lead  the  inexperienced  reader 
to  conclude  that  by  the  use  of  any  seed  products,  or 
other  food-stuffs  of  vegetable  origin,  whose  func- 
tions are  those  of  storage  organs,  that  diets  can  be 
prepared  which  are  so  satisfactory  as  to  make  it 
feasible  to  dispense  with  a  liberal  intake  of  the  food- 
stuffs which  we  have  designated  as  protective  foods. 
These  can  be  shown  to  be  based  upon  failure  to  fully 
appreciate  what  constitutes  a  satisfactory  demon- 
stration of  the  adequacy  of  a  diet.  Mankind  will  do 
well  to  avoid  such  diets  which  may,  as  Golderger 
has  suggested,  place  one  in  ^^a  Hwilight'  zone  within 
which  a  very  slight  change  in  any  of  the  dietary 
components  may  cause  an  important  shift  of  bal- 
ance." 

McCollmn  and  Simmonds  have  reported  many 
experiments  T^ith  diets  so  planned  as  to  be  satisfac- 
toiy  in  that  all  the  factors  but  one  afforded  a  Uberal 
margin  of  safety  in  offermg  an  abundance  over  the 
ninimal  requkements  of  the  animal,^  and  the  re- 
maining one  so  adjusted  as  to  represent  the  actual 


148    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

niiiiimum  on  which  the  animal  can  subsist  over  a 
considerable  period.  In  this  way  it  has  been  possible 
to  demonstrate  that  the  amount  of  fat-soluble  A 
may  be  reduced  to  a  certain  minimum  without  the 
development  of  xerophthalmia,  whereas  the  same 
intake  of  this  substance  will  not  prevent  the  charac- 
teristic eye  trouble  when  the  intake  of  protein  is 
likewise  sufficiently  lowered.  They  have  been  able 
to  so  adjust  the  components  of  the  diet  as  to  make 
it  possible  to  reheve  xerophthalmia  either  by  in- 
creasing the  content  of  protein  or  of  fat-soluble  A 
in  the  food,  although  it  is  the  lack  of  the  latter  which 
is  the  specific  cause  of  the  disease.  Such  observations 
make  it  evident  that  it  is  impossible  to  say  what  is 
the  safe  minimum  of  any  dietary  factor,  unless  the 
biological  values  of  all  the  other  essential  constituents 
of  the  diet  are  knowTi.  This  represents  an  actual 
accompHshment  of  planning  a  diet  which  brings 
the  animal  into  the  'Hwihght"  zone,  w^here  small 
shifts  in  the  quality  of  the  diet  with  respect  to  any 
factor  may  either  distinctly  stabilize  the  metabolic 
processes  of  the  animal,  or  may  lead  to  the  develop- 
ment of  a  distinct  pathologic  state. 

Their  studies  with  the  types  of  diets  just  described, 
lead  them  to  the  conclusion  that  it  is  unwise  to 
approach  very  closely  the  physiological  minimum 
with  respect  to  any  dietary  factor.  Liberal  consump- 
tion of  all  of  the  essential  constituents  of  a  normal  diet, 
prompt  digestion  and  absorption  arid  prompt  evacuation 
of  the  undigested  residue  from  the  intestine  before  ex- 


THE  PLANNING  OF  THE  DIET  149 

tensive  absorption  of  products  of  bacterial  decomposition 
of  proteins  can  take  place,  are  the  optimum  conditions 
for  the  maintenance  of  vigor  and  the  characteristics 
of  youth.  Such  a  dietary  regime  can  be  attained  only 
by  supplementing  the  seed  products,  tubers,  roots 
and  meat,  which  must  constitute  the  bulk  of  the 
diet  of  man,  with  the  protective  foods,  milk  and  the 
leafy  vegetables. 

The  results  of  the  study  of  several  representatives 
of  each  of  the  different  classes  of  food-stuffs  has  led 
the  author  to  the  conclusion  that,  while  it  is  not  de- 
sh^able  to  relegate  to  the  background  any  of  ihe 
fundamental  knowledge  of  food-stuffs  which  can  be 
obtained  by  chemical  methods,  and  by  resphation 
and  digestion  studies,  the  fundamental  basis  of  nutri- 
tion can  best  be  imparted  to  the  public  tlii'ough  the 
adoption  of  a  biological  classification  of  the  natural 
food-stuffs  on  the  basis  of  their  function.  Foods 
other  than  milk  and  eggs  of  both  animal  and  veg- 
etable origin  may  be  arranged  into  groups  according 
to  whether  they  represent  principally,  functioning 
active  protoplasm,  or  deposits  of  reserve  food  mate- 
rial, or  in  animal  tissues,  highly  speciahzed  contract- 
ile tissues.  From  their  biological  function  their 
dietaiy  properties  can  be  fairly  accurately  predicted. 
This  idea,  together  with  the  knowledge  that  milk, 
eggs  and  the  leafy  vegetables,  the  protective  foods, 
are  so  constituted  as  to  correct  the  dietary  deficiencies 
of  the  seeds,  tubers,  roots  and  meat,  should  form 
the  central  idea  in  the  teaching  of  the  science  of 


150    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

nutrition.  It  should  be  emphasized  that  the  diet  is 
a  relatively  complex  thing,  and  that  none  of  the 
essential  constituents  can  be  ignored  in  its  planning, 
but  that  the  observance  of  certain  general  rules  of 
procedure  will  insure  that  any  faults  in  the  dieli 
will  be  reduced  to  a  minimum. 

It  is  of  special  moment  at  this  time  to  emphasize 
the  importance  of  the  dairy  industry  in  its  relation 
to  the  pubUc  health.  Mankind  may  be  roughly 
classified  into  two  groups.  Both  of  these  have  de- 
rived the  greater  part  of  their  food  supply  from 
seeds,  tubers,  roots  and  meat,  but  have  differed  in 
respect  to  the  character  of  the  remainder  of  their 
diets.  One  group,  represented  by  the  Chinese, 
Japanese  and  the  peoples  of  the  Tropics  generally, 
have  employed  the  leaves  of  plants  as  almost  their 
sole  protective  food.  They  likewise  eat  eggs  and 
these  serve  to  correct  their  diet.  The  other  group 
includes  the  peoples  of  Europe  and  North  America 
and  a  few  others.  These  have  likewise  made  use 
of  the  leaves  of  plants,  but  in  lesser  degree,  and  have, 
in  addition,  derived  a  very  considerable  part  of  their 
food  supply  from  milk  and  its  products. 

Those  peoples  who  have  employed  the  leaf  of  the 
plant  as  their  sole  protective  food  are  characterized 
by  small  stature,  relatively  short  span  of  life,  high 
infant  mortality,  and  by  contended  adherence  to  the 
em.ployment  of  the  simple  mechanical  inventions  of 
their  forefathers.  The  peoples  who  have  made  hb- 
eral  use  of  milk  as  a  food,  have,  in  contrast,  attained 


THE  PLANNING  OF  THE  DIET  151 

greater  size,  greater  longe\dty,  and  have  been  much 
more  successful  in  the  rearing  of  their  young.  They 
have  been  more  aggressive  than  the  non-milk  using 
peoples,  and  have  achieved  much  greater  advance- 
ment in  Uteratm'e,  science  and  art.  They  have 
developed  in  a  higher  degree  educational  and  poUt- 
ical  systems  which  offer  the  greatest  opportunity 
for  the  mdividual  to  develop  his  powers.  Such 
development  has  a  physiological  basis,  and  there 
seems  eveiy  reason  to  beheve  that  it  is  fundamentally 
related  to  nutrition. 

In  the  United  States,  w^e  have  in  the  past  de- 
rived no  less  than  15  to  20  per  cent  of  our  total 
food  supply  from  the  products  of  the  dairy.  The 
investigations  of  recent  years  have  thrown  a  new 
light  on  the  importance  of  tliis  increment  of  our  diet. 
It  has  become  evident  that  milk  is  the  greatest 
factor  of  safety  m  our  nutrition,  and  it  is  certain 
that  we  could  not  have  accomphshed  what  we  have, 
had  we  dispensed  with  milk  as  a  food. 

The  situation  of  the  daiiy  industr>^  is  at  the  present 
time  precarious.  The  cost  of  feeding-stuffs  and  of 
labor  have  enormously  increased  during  the  last 
few  years,  and  consequently  the  cost  of  milk  produc- 
tion. Advance  in  the  cost  of  milk  to  the  consumer 
has  been  made  unavoidable.  Every  advance  in  the 
price  has,  however,  met  with  great  resistance  by  the 
pubUc,  and  with  each  rise  there  has  been  a  distinct 
drop  in  the  amount  purchased.  The  milk  dehvered 
in  the  city  of  Chicago  has  fallen  off  from  about  a 


152    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

million  and  a  quarter  quarts  daily  to  about  seven 
hundred  thousand  quarts,  within  a  year.  Similar 
reductions  in  sales  have  occurred  almost  everywhere 
in  the  Eastern  half  of  the  country,  solely  because  of 
the  rise  in  pi  ice.  This  has  resulted  in  the  discourage- 
ment of  producers  ever>^vhere,  and  in  a  movement 
toward  the  reduction  of  the  number  of  dairy  cows. 

There  can  be  no  doubt  that  there  is  great  lack  of 
knowledge  by  the  people  generally  as  to  the  impor- 
tance of  milk  and  other  dairy  products  in  the  diet. 
There  is  no  substitute  for  milk,  and  its  use  should 
be  distinctly  increased  instead  of  diminished,  re- 
gardless of  cost.  Every  possible  means  should  be 
employed  to  reduce  the  cost  of  distribution.  The 
necessity  for  the  liberal  use  of  milk  and  its  products 
both  in  the  diets  of  children  and  adults  should  be 
emphasized  in  order  to  stem  the  ebbing  tide  of  its 
production.  It  has  been  pointed  out  that  the  value 
of  milk  as  a  food  cannot  be  estimated  on  the  basis 
of  its  content  of  protein  and  energy.  Even  when 
measured  by  this  standard  it  compares  most  favor- 
ably with  other  foods,  but  it  has  a  value  as  a  protect- 
ive food,  in  improving  the  quaUty  of  the  diet,  which 
can  be  estimated  only  in  terms  of  health  and  effi- 
ciency. 

An  examination  of  any  large  groups  of  people  in 
the  cities,  will  show  that  where  there  is  a  high  mor- 
tahty  from  tuberculosis,  milk  is  not  being  used  to 
any  great  extent,  and  in  any  large  group  where 
milk  purchases  are  large  this  disease  is  not  a  menace. 


THE  PLANNING  OF  THE  DIET  153 

It  is  well  known  that  in  institutions  where  tuber- 
culosis is  successfully  treated  milk  forms  the  prin- 
cipal article  of  the  diet  of  the  inmates.     This  has 
resulted  from  cHnical  experience.    There  is  no  other 
effective  treatment  for  this  disease   than   that  of 
providing  fresh  air,  insisting  upon  rest  and  of  height- 
ening the  body's  powers  of  resistance  through  the 
liberal  use  of  milk  for  the  correction  of  faults  which 
the  diet  ^\ill  inevitably  have  when  it  consists  too 
largely  of  seed  products,  tubers,  roots  and  meats. 
The  importance  of  diets  of  this  character  in  the 
etiology    of    tuberculosis,    has    not    hitherto    been 
appreciated.    In  the  light  of  facts  presented  in  the 
previous   chapters  of  this  book,   there   can  be  no 
reasonable    doubt    that    the    miportance    of    poor 
hygienic   conditions  and  of  poor  ventilation  have 
been  greatly  over-estimated,  and  that  of  poor  diet 
not  at  all  adequately  appreciated  as  factors  in  pro- 
moting the  spread  of  this  disease.     i\Iilk  is  just  as 
necessaiy  in  the  diet  of  the  adult  as  in  that  of  the 
growing  child.     Any  diet  which  will  not  support 
normal  development  in  the  young  will  not  support 
optimum  well-being  in  the  adult.    ]Milk  is  our  greatest 
protective  food,  and  its  use  must  be  increased.    The 
price  must  be  allowed  to  go  up,  so  long  as  the  cost 
of  production  makes  it  necessary,  and  up  so  far  as  is 
essential  to  make  milk  production  a  profitable  busi- 
ness.   Unless  this  is  done,  the  effects  will  soon  be- 
come apparent  in  a  lowermg  of  our  standards  of 
health  and  efficiency. 


INTRODUCTION  TO  THE  LEGENDS  TO  THE 

CHARTS 

The  data  upon  which  the  foregoing  discussion  of 
diet  is  based,  consists  of  about  three  thousand  feeding 
experiments.  Most  of  these  were  carried  out  with 
domestic  rats,  but  in  order  to  demonstrate  the  gen- 
eral apphcabihty  of  the  results  of  tests  made  on  one 
species  to  other  species  of  animals,  numerous  feeding 
tests  were  made  on  farm  pigs,  cattle,  chickens, 
guinea  pigs  and  a  few  on  pigeons.  These  all  indicate 
that  the  chemical  requirements  of  these  different 
types  of  animals  are  essentially  the  same.  The 
following  charts  present  the  growth  curves  of  rats, 
fed  a  series  of  diets  which  illustrate  the  type  of  re- 
sults from  which  the  conclusions  in  this  book  are 
drawn.  In  each  case  the  curve  is  the  actual  record 
of  an  individual  which  fairly  represents  the  behavior 
of  from  four  to  six  or  mxore  animals. 

The  broken  curve  marked  N  with  the  sex  sign 
(cf  =  male;  9  =  female)  represents  the  normal  ex- 
pectation of  growth  in  each  sex  when  fed  a  mixed 
diet  containing  several  seeds  and  a  liberal  supply 
of  milk.  Vertically  the  curves  designate  body  weight ; 
horizontally  from  left  to  right  the  charts  record 
duration  of  experiment,   each  square  representing 

154 


LEGENDS  TO  THE  CHARTS  155 

four  weeks.    A  break  in  a  curve  marked  Y,  indicates 
the  birth  of  a  litter  of  young. 

Although  experiments  are  described  only  for  the 
wheat,  rice  and  oat  kernel  among  the  seeds,  similar 
records  are  available  for  all  the  m.ore  important 
seeds  used  as  foods  in  America,  and  these  warrant 
the  statement  that  seeds  as  a  class  closely  resemble 
each  other  in  their  dietary  properties.  A  close  re- 
semblance like^vise  exists  among  the  several  leaves 
which  have  been  studied,  so  that  the  edible  leaves 
may  be  regarded  as  having  in  a  general  way  the  sam^e 
dietary  properties. 

Chart  1. — Lot  417  shows  the  results  of  restricting  young  rats  to 
a  diet  of  purified  protein,  salts,  carbohydrate  and  agar-agar,  together 
with  an  extract  of  a  natural  food-stuff  which  furnishes  the  dietary 
factor,  water-soluble  B,  the  substance  which  prevents  beri-beri. 
The  diet  was  complete  except  for  the  absence  of  the  fat-soluble  A. 
As  a  rule  there  develops  in  animals  so  fed,  a  tj^pe  of  xerophthalmia, 
which  is  due  to  the  lack  of  the  fat-soluble  A.  When  a  fat  or  other 
natural  food  which  is  rich  in  cellular  structures  (as  contrasted  with 
reserve  food  materials),  is  added  to  a  food  mixture  of  this  tyj)e,  the 
resulting  diet  becomes  capable  of  inducing  growth. 

Lot  418,  Period  1,  shows  the  curves  of  body  weight  of  rats  fed  a  diet 
similar  to  that  described  above  for  Lot  417,  but  differing  in  that  it 
contained  butter  fat  (fat-soluble  A)  but  lacked  the  extract  of  natural 
foods,  and,  therefore,  contained  no  water-soluble  B.  On  this  diet 
xerophthalmia  does  not  develop,  but  the  animals  ultimately  lose 
muscular  control  and  manifest  symptoms  suggestive  of  beri-beri  in 
man.  Growth  is  not  possible  on  this  diet,  but  everything  which  is 
needed  in  the  diet  so  far  as  chemical  analysis  could  show,  is  present. 

These  results  show  the  necessity  of  a  biological  analysis  of  food- 
stuffs. Gro^vth  at  once  took  place  when,  in  Period  2,  the  dietary 
essential  water-soluble  B,  which  is  likewise  soluble  in  alcohol,  was 
added  to  the  diet.    This  dietary  factor  is  abundant  in  all  natural 


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LEGENDS  TO  THE  CHARTS  157 

foods.  In  investigations  of  the  nature  of  those  here  described,  it  is 
usually  added  as  an  alcoholic  extract  of  a  natural  food. 

Lot  419  shows  the  type  of  growth  curves  secured  with  diets  con- 
taining both  fat-soluble  A  and  water-soluble  B,  in  addition  to  the 
long  recognized  food  substances,  protein,  carbohydrate,  fat  and  a 
satisfactory  supply  of  the  inorganic  elements  essential  for  the  nutri- 
tion of  an  animal.  There  is  much  reason  to  believe  that  each  of  the 
two  unidentified  dietary  factors  A  and  B  contains  but  a  single  chem- 
ical complex  which  is  physiologically  indispensable,  and  not  a  group 
of  such  substances. 

Chart  2. — This  chart  illustrates  the  nature  of  the  dietary  defi- 
ciences  of  the  cereal  grains,  as  revealed  by  feeding  a  single  variety 
of  seed  with  the  addition  of  certain  purified  food  substances.  Wheat 
is  a  typical  representative  of  the  group  of  seeds. 

The  wheat  kernel  when  fed  as  the  sole  source  of  nutriment,  or  when 
supplemented  with  protein  alone  or  with  fat-soluble  A  alone  (in 
butter  fat),  does  not  induce  any  growth  in  a  young  animal.  Wheat 
supplemented  with  the  three  inorganic  elements,  calcium,  sodium 
a-nd  chlorine,  and  with  no  other  additions,  induces  slow  growth  for 
a  time.  In  other  words,  the  salt  content  is  the  first  limiting  factor 
in  seeds  from  the  dietary  standpoint.  These  facts  are  not  illustrated 
by  growth  curves. 

Lot  223  illustrates  the  growth  of  young  rats  when  fed  wheat  to- 
gether with  two  purified  food  additions,  viz.,  protein  and  a  salt 
mixture  of  suitable  composition.  The  dextrinized  starch  in  this  diet 
has  no  special  significance.  On  this  diet  animals  may  grow  to  nearly 
the  full  adult  size  at  the  normal  rate,  and  in  some  cases  a  small  litter 
of  young  may  be  produced.  The  young  as  a  rule  wiU  be  allowed  to 
die  within  a  few  days.  On  such  a  diet  xerophthalmia  will  ultimately 
develop,  and  this  forms  the  terminal  event  in  the  lives  of  the  animals. 
This  shows  that  the  content  of  fat-soluble  A  in  wheat  is  below  the 
amount  required  to  maintain  an  animal  in  a  state  of  health  over  a 
long  period.  This  fact  is  further  illustrated  by  the  record  of  rat 
223-B,  whose  diet  was  Uke  that  of  223,  except  that  the  former  con- 
tained 5  per  cent  of  butter  fat.  Butter  fat  is  the  best  known  source 
of  fat-soluble  A. 

Lot  380,  Period  1,  shows  how  slowly  growth  proceeds  when  the 
diet  consists  of  wheat,  supplemented  with,  two  purified  food  addi- 
tions, protein  and  fat-soluble  A  (as  butter  fat).     The  deficiency  of 


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LEGENDS  TO  THE  CHARTS  159 

the  wheat  kernel  in  certain  inorganic  elements  is  illustrated  by  the 
great  acceleration  of  growth  in  Period  2,  when  a  suitably  constituted 
salt  mixture  was  added  to  the  diet  of  Period  1. 

Lot  319  shows  the  slow  growth  of  a  rat  when  fed  wheat  supple- 
mented only  with  the  requisite  inorganic  salts  and  fat-soluble  A. 
The  proteins  of  the  wheat  kernel  are  not  of  very  good  quality,  and 
must  be  enhanced  by  further  protein  additions  before  growth  can  be 
normal. 

Lot  223-B  illustrates  the  fact  that  the  optimum  rate  of  growth  is 
secured  with  wheat  supplemented  with  three  purified  food  addi- 
tions, viz.,  salts,  fat-soluble  A  and  protein.  When  wheat  is  improved 
with  respect  to  these  three  dietary  factors,  it  becomes  a  complete 
food,  and  supports  the  production  of  the  normal  number  of  young, 
and  the  young  are  successfully  reared.  What  is  true  of  wheat  is 
hkewise  true  in  a  general  way  of  the  other  seeds.  Seeds  are  similar 
in  their  dietary  properties.  In  other  words,  the  mineral  content  of 
any  seed  must  be  improved  by  suitable  salt  additions,  its  protein 
content  must  be  enhanced  by  the  addition  of  other  proteins  which 
yield  in  greater  abundance  those  amino-acids  which  it  yields  in  small 
amounts,  and  in  most  cases  additional  fat-soluble  A  must  be  added 
in  order  to  prevent  the  ultimate  development  of  a  pathological  con- 
dition of  the  eyes.  A  liberal  supply  of  milk  will  correct  all  the  defi- 
ciencies of  a  seed  diet. 

Chart  3. — In  the  process  of  polishing,  both  the  germ  and  the  bran 
layer  of  the  rice  kernel  are  rubbed  off,  thus  removing  the  cellular 
structures  and  leaving  only  the  endosperm.  This  consists  almost 
entirely  of  proteins,  starch,  a  small  amount  of  fats,  and  of  mineral 
elements  in  the  form  of  salts.  Its  proteins  are  of  relatively  low  value 
for  inducing  growth.  Polished  rice  is,  therefore,  practically  com- 
parable, from  the  dietary  standpoint,  to  the  diet  of  purified  food- 
stuffs described  in  Chart  1. 

Lot  317  shows  the  behavior  of  young  rats  which  were  fed  polished 
rice  supplemented  with  two  dietary  factors,  viz.,  a  suitable  salt 
mixture  and  fat-soluble  A.  This  does  not  support  growth,  since  the 
diet  is  still  deficient  in  two  respects.  It  lacks  the  second  dietary 
essential,  water-soluble  B,  and  its  proteins  are  of  too  poor  quality 
for  the  support  of  growth  in  the  amount  supplied  by  90  per  cent  of 
rice.  Such  a  diet  as  that  of  Lot  317  will  permit  the  development 
of  a  condition  in  rats  similar  to  beri-beri  in  man. 


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LEGENDS  TO  THE  CHARTS  161 

Lot  324  shows  the  effects  on  young  rats  of  feeding  them  on  a 
mixture  consisting  of  poHshed  rice  supplemented  with  purified  pro- 
tein, a  suitable  salt  mixture  and  fat-soluble  A.  The  pohshed  rice 
evidently  contains  some  cellular  elements  and,  therefore,  some  of  the 
water-soluble  B,  for  the  animals  were  able  to  grow  very  slowly  in 
some  cases,  and  to  remain  aUve  during  several  months.  Lot  401 
illustrates  the  remarkable  effects  of  adding  to  this  diet  an  alcoholic 
extract  of  wheat  germ.  This  extract  furnished  a  Hberal  amount  of 
water-soluble  B  (likewise  soluble  in  alcohol)  and  renders  the  diet 
complete.  The  alcohol  was  employed  to  dissolve  this  dietary  essen- 
tial from  the  germ,  and  was  evaporated  completely  before  the  ration 
was  fed. 

Lot  383  shows  the  dietary  properties  of  unpolished  as  contrasted 
with  pohshed  rice.  The  former  which  contains  the  cellular  struc- 
tures of  the  germ  and  the  bran  layer,  is  rendered  complete  as  a  food 
by  the  addition  of  protein,  fat-soluble  A  and  salts.  Young  rats  do 
not  grow  at  all  when  fed  solely  upon  unpohshed  rice,  without  these 
additions.  Unpohshed  rice  closely  resembles  wheat,  corn,  rye, 
barley  and  other  seeds  in  its  dietary  properties. 

Lot  401  shows  the  behavior  of  young  animals  when  fed  polished 
rice  supplemented  in  four  respects,  viz.,  protein,  a  suitable  salt 
mixture,  fat-soluble  A  and  water-soluble  B.  On  this  diet,  young  rats 
grew  to  the  normal  adult  size,  reproduced  repeatedly  and  were  able 
to  rear  a  few  of  their  young.  The  omission  of  any  one  of  these  addi- 
tions would  lead  to  almost  complete  failure  of  young  animals  to 
develop  on  this  diet. 

These  examples  make  clear  the  method  of  procedure  in  making  a 
biological  analysis  of  a  food-stuff.  The  latter  consists  of  a  suitably 
planned  series  of  feeding  experiments  in  which  single  and  multiple 
purified  food  additions  are  made  to  a  single  natural  food-stuff,  and 
observations  are  made  as  to  the  ability  of  young  animals  to  grow 
and  perform  the  functions  of  adult  life  on  the  resulting  food  mixtures. 
In  this  way  information  can  be  secured  which  chemical  methods 
are  unable  to  reveal. 

Chart  4. — These  records  illustrate  the  biological  analysis  of  the 
dietary  properties  of  the  oat  kernel  (rolled  oats).  Lots  623  and  654 
show  the  failure  of  young  rats  to  grow  on  rolled  oats  supplemented 
with  either  a  suitable  inorganic  mixture,  or  with  purified  protein 
as  the  only  addition.    Correction  of  these  factors  is  necessary,  but 


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LEGENDS  TO  THE  CHARTS  163 

there  are  still  other  faults  in  the  oat  kernel  which  must  be  corrected 
before  it  becomes  a  complete  food.  This  is  illustrated  by  the  re- 
maining records  in  this  chart. 

Lot  625  shows  that  when  the  oat  kernel  is  supplemented  with 
both  a  suitable  salt  mixture  and  fat-soluble  A,  it  can  support  growth 
at  a  good  rate  for  three  months,  but  does  not  permit  the  animal  to 
reach  full  adult  size,  and  leads  to  early  failure.  The  protein  of  the 
oat  kernel  has  a  slightly  higher  value  for  growth  than  has  that  of 
either  wheat  or  corn,  but  the  amount  furnished  by  90  per  cent  of 
rolled  oats  is  below  the  optimum  for  the  support  of  growth  in  a 
rapidly  growing  species.  A  diet  rich  in  rolled  oats  produces  very 
hard,  pasty  feces,  which  are  difficult  of  ehmination.  This  appears 
to  be  a  factor  of  importance  in  preventing  the  normal  development 
of  the  experimental  animals  in  this  series. 

Lot  624  further  illustrates  the  inadequacy  of  rolled  oats  sup- 
plemented with  both  a  suitable  salt  mixture  and  protein  (casein). 
This  food  mixture  lacks  a  sufficient  amount  of  fat-soluble  A,  and 
unless  there  is  an  addition  of  this  substance,  the  animals  always 
develop  the  eye  trouble  (xerophthalmia)  described  on  page  87. 

Lot  655,  shows  the  growth  curve  of  an  animal  fed  rolled  oats 
supplemented  with  protein,  an  appropriate  mineral  salt  mixture  and 
fat-soluble  A.  In  this  case  the  protein  employed  was  casein  of  milk. 
This  ration  is  dietetically  complete,  so  far  as  its  chemical  composition 
is  involved,  but  it  did  not  support  normal  development  to  the  full 
adult  size.  It  is  not  possible  to  state  just  how  far  the  stunting  was 
due  to  the  pasty  character  of  the  feces  formed  from  this  diet,  and 
how  far  the  results  should  be  attributed  to  the  failure  of  casein  to 
supplement  the  amino-acid  deficiencies  of  the  oat  proteins.  Much 
better  nutrition  is  secured  with  this  diet  when  the  casein  is  replaced 
by  another  protein,  gelatin,  as  is  shown  by  the  records  of  Lot  647. 

Lot  647  illustrates  the  completeness  of  a  diet  derived  from  rolled 
oats  supplemented  with  an  appropriate  salt  mixture,  fat-soluble  A 
and  the  protein,  gelatin.  When  Charts  2,  3  and  4  are  compared, 
they  show  the  striking  similarity  from  the  dietary  standpoint  of  the 
three  seeds,  wheat,  rice  (unpolished)  and  oat  kernels. 

It  is  not  to  be  concluded  from  these  experiments  which  show  the 
faulty  character  of  these  seeds  as  foods,  that  they  are  undesirable 
constituents  of  the  diet.  Neither  is  it  necessary  or  practicable  to 
supplement  in  practice  the  seeds  which  we  eat  \sdth  additions  of 


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LEGENDS  TO  THE  CHARTS  165 

protein,  salts,  etc.,  in  the  manner  employed  in  the  biological  analysis 
of  these  which  we  have  described.  There  are  two  classes  of  protective 
foods,  milk  and  the  leafy  vegetables,  which  when  taken  along  with 
the  seeds  and  their  products,  make  good  their  deficiencies,  and  render 
the  diet  complete.  These  correct  the  inorganic  deficiencies  (calcium, 
sodium  and  chlorine),  insure  a  sufficient  amount  of  fat-soluble  A,  and 
etihance  the  value  of  the  proteins  of  the  seed. 

Chart  5. — Each  of  the  more  important  seeds  which  are  employed 
in  human  and  animal  nutrition,  have  been  studied  by  the  methods 
employed  for  wheat,  rice  and  the  oat  kernel,  and  the  results  show 
that  the  seeds  all  resemble  each  other  in  a  general  way  in  their  dietary 
properties.  They  all  require  the  same  kinds  of  supplementary  addi- 
tions to  make  them  complete  foods.  It  would  be  expected,  therefore, 
that  mixtures  of  any  seeds  should  not  form  complete  diets.  The 
following  experiments  demonstrate  that  this  is  indeed  the  case. 

Lot  722  shows  the  failure  of  animals  to  grow  when  confined  to  a 
mixture  of  corn  and  flaxseed  oil  meal.  After  nearly  four  months  of 
stunting  there  was  an  immediate  response  with  growth  when  the 
inorganic  content  of  the  diet  was  supplemented  with  a  suitable  salt 
mixture. 

^Mixtures  of  seeds  will,  in  nearly  all  cases,  furnish  proteins  in 
greater  value  than  those  of  the  individual  seeds  fed  singlj',  since  the 
amino-acids  in  which  they  are  relatively  deficient  are  not  the  same 
in  different  seeds.  The  seeds  all  contain  some  of  the  fat-soluble  A, 
but  not  as  much  as  is  desirable  in  the  diet.  In  seed  mixtures  there 
is  only  a  relative  shortage  of  this  dietary  essential.  The  deficiency 
of  certain  inorganic  elements  is,  therefore,  the  first  limiting  factor 
in  mixtures  of  seeds  as  food-stuffs.  In  many  of  the  growth  curves 
exhibited  in  the  charts,  complex  salt  mixtures  were  added,  since  at 
the  time  the  experiments  were  carried  out,  our  knowledge  concerning 
the  inorganic  factor  was  still  very  incomplete.  It  is  now  known  that 
but  three  elem^ents  need  be  added  to  seed  mixtures,  viz.,  calcium, 
sodium  and  chlorine. 

Lot  713  shows  the  failure  of  five  seeds  to  support  growth.  In 
Period  2,  the  correction  of  the  inorganic  deficiencies  of  the  diet  was 
followed  by  a  prompt  response  with  growth.  The  poor  quality  of  the 
proteins  and  relative  shortage  of  fat-soluble  A,  will  in  time  lower  the 
vitahty  of  animals  fed  such  a  seed  mixture,  when  only  the  inorganic 
factor  is  corrected. 


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LEGENDS  TO  THE  CHARTS  167 

Lot  959  shows  that  the  addition  of  fat-soluble  A  (as  butter  fat) 
to  a  mixture  of  three  seeds,  wheat,  corn  and  oats,  does  not  produce 
a  food  which  can  support  growth  except  at  a  very  slow  rate.  In 
Period  2,  the  correction  of  the  inorganic  deficiencies  of  the  diet  was 
followed  by  a  prompt  response  with  growth. 

Lot  1012,  in  Period  1,  received  three  seeds  supplemented  -with 
both  protein  (casein)  and  fat-soluble  A,  but  could  not  grow  on  this 
diet.  In  Period  2,  the  addition  of  the  necessary  salts  produced  an 
immediate  response  with  growth. 

Lot  714-B,  which  were  fed  three  seeds,  suffered  complete  suspen- 
sion of  growth.  There  was  no  response  in  Period  2,  to  the  addition 
of  fat-soluble  A  in  butter  fat.  Although  both  protein  and  fat- 
soluble  A  are  desirable  additions  to  any  seed  diet,  and  are  necessary 
before  the  optimum  nutrition  can  be  attained,  the  inorganic  defi- 
ciencies must  be  corrected  before  any  noticeable  benefit  can  be  de- 
rived from  the  correction  of  the  other  factors.    (Compare  959-714-B.) 

Chart  6. — In  marked  contrast  to  the  failure  of  young  animals  to 
grow  on  a  diet  restricted  to  seeds,  one  can  secure  very  satisfactory 
rations  from  mixtures  of  leaf  and  seed.  The  leaf  is  a  cell  rich  struc- 
ture; the  seed,  a  cell  poor  storage  organ.  With  this  difference  in 
function  go  corresponding  differences  in  dietary  properties.  (See 
pages  43-44.) 

These  curves  illustrate  the  relative  values  for  the  support  of  growth 
and  reproduction  of  diets  derived  from  alfalfa  leaf  flour  40  per  cent, 
and  a  seed  60  per  cent.  It  will  be  seen  that  these  corresponding  leaf 
and  seed  mixtures  are  not  of  equal  value.  In  a  general  way  the  leaves 
all  resemble  each  other  in  their  dietary  properties,  and  form  a  dis- 
tinct group  of  food-stuffs  as  do  the  seeds. 

Lot  685  shows  the  possibility  of  securing  a  normal  growth  curve 
and  repeated  reproduction  with  a  rat  restricted  to  a  mixture  of  alfalfa 
leaf  flour  40  per  cent  and  rolled  oats  60  per  cent.  Of  the  six  litters 
(33  young)  borne  by  mothers  which  had  grown  up  on  this  diet,  16 
young  or  50  per  cent  were  successfully  reared  to  weaning  time. 
Despite  the  fact  that  an  animal  can  grow  at  a  rate  which  we  may 
regard  as  normal  on  this  food  mixture,  it  is  not  of  a  highly  satisfactory 
character.  Rolled  oats  and  alfalfa  leaf  make  a  better  diet  than  the 
alfalfa  leaf  with  any  other  seed  which  we  have  studied.  It  is  inter- 
esting that  these  proportions  between  alfalfa  leaf  and  rolled  oats  give 
better  results  in  the  nutrition  of  the  rat  than  any  others. 


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LEGENDS  TO  THE  CHARTS  169 

Lots  687  and  686,  show  that  there  is  Httle  difference  in  the  values 
of  mixtures  of  the  alfalfa  leaf  with  the  wheat  kernel  as  compared 
with  the  corn  kernel.  Both,  in  the  proportions  here  employed,  fail 
to  induce  growth  at  the  "normal"  rate,  and  the  number  of  j^oung 
produced  was  approximately  one-fifth  that  which  a  female  rat  vdW 
produce  when  her  diet  is  of  excellent  quality.  A  well-nourished 
female  rat  may  be  expected  to  produce  five  htters  of  young. 

Lot  478  shows  that  even  with  a  simple  mixture  of  alfalfa  leaf 
flour  40  per  cent  and  polished  rice  60  per  cent,  rats  were  able  to  grow 
to  about  83  per  cent  of  the  normal  adult  size  and  to  produce  3'oung. 
The  rat  whose  curve  is  shown  had  two  htters.  All  young  from 
mothers  which  had  grown  up  on  this  diet  were  allowed  to  die  during 
the  first  few  days  after  birth. 

Lots  688  and  717,  show  that  combinations  of  peas  or  of  cottonseed 
with  the  alfalfa  leaf  flour  form  food  mixtures  which  can  support 
growth  at  a  slow  rate,  but  are  inferior  to  certain  other  combinations 
of  leaf  and  seed. 

There  are  very  great  possibilities  for  improving  our  practices  in 
the  utiUzation  of  feeding-stuffs  in  animal  production.  We  need 
exact  knowledge  regarding  the  best  combinations  and  proportions 
in  which  to  feed  our  natural  products. 

Chart  7. — It  is  easily  possible  to  prepare  diets  which  are  derived 
solely  from  vegetable  sources,  which  will  induce  growth  from  weaning 
time  to  full  adult  size  and  support  the  production  of  young.  Success 
in  this  direction  involves  the  emplojTnent  of  suitable  combinations 
of  leaves,  together  with  foods  of  plant  origin  whose  functions  are 
those  of  storage  organs,  \dz.:  seeds,  tubers,  and  roots.  The  records 
here  presented  show  the  most  successful  results  which  we  have  ob- 
tained with  mixtures  of  leaf  and  seeds. 

Lot  273  shows  the  results  of  restricting  young  rats  from  weaning 
time  to  a  diet  derived  entirely  from  the  alfalfa  leaf  flour,  corn  and 
peas.  The  peas  were  cooked  at  15  pounds  pressure  for  one  hour  in  an 
autoclave.    The  other  constituents  of  the  diet  were  fed  raw. 

The  female  rat  marked,  First  Generation,  never  grew  to  the  full 
adult  size,  but  others  in  the  same  cage  with  her  did.  The  curve  of 
this  particular  rat  is  presented  because  she  became  the  great  grand- 
mother of  a  litter  whose  ascendants  for  four  generations  ate,  beyond 
the  weaning  age,  nothing  but  this  monotonous  mixture  of  vegetable 
foods. 


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LEGENDS  TO  THE  CHARTS  171 

This  ration  did  not  induce  optimum  nutrition.  The  number  of 
young  produced  was  approximately  half  what  well-fed  rats  normally 
produce,  and  the  mortality  of  the  young  was  high.  Although  the 
breeding  records  were  poor  and  the  litters  small,  most  of  these  young 
were  reared.  Notwithstanding  this,  the  vigor  of  the  fourth  genera- 
tion appeared  to  be  as  great  as  that  of  the  first. 

The  above  mixture  gives  better  results  in  the  nutrition  of  the  rat 
than  any  other  proportions  in  which  these  three  food-stuffs  can  be 
combined.  If  the  amount  of  alfalfa  leaf  is  raised  to  40  per  cent  or 
reduced  to  20  per  cent,  and  the  content  of  corn  is  reduced  or  increased 
respectively,  few  young  will  be  reared.  The  importance  of  knowing 
the  exact  proportions  in  which  to  combine  our  natural  food-stuffs 
in  order  to  secure  the  optimum  results  in  nutrition,  especially  in 
animal  production,  will  be  evident  from  these  results. 

Chart  8. — Tliis  chart  affords  an  illustration  of  the  great  differences 
in  the  degree  in  which  a  supplementary  addition  of  protein  may  en- 
hance the  value  of  the  proteins  of  a  natural  food-stuff.  The  curves 
should  be  considered  in  pairs. 

Lot  493  shows  the  results  of  feeding  a  diet  deriving  its  protein 
content  entirely  from  the  wheat  kernel.  The  diet  contained  but  7 
per  cent  of  protein,  an  amount  too  small  because  of  the  relatively 
poor  quality  of  the  wheat  proteins,  to  support  growth  at  the  optimum 
rate.  The  group  of  rats  which  were  fed  this  diet  grew  at  about  half 
the  normal  rate. 

Lot  652  received  the  same  diet,  with  10  per  cent  of  the  carbo- 
hydrate replaced  by  the  protein  gelatin.  The  latter  is  one  of  the 
"incomplete"  proteins,  since  it  lacks  three  of  the  amino-acids  which 
are  essential  for  the  nutrition  of  an  animal.  A  diet  which  contains 
gelatin  as  its  sole  protein,  no  matter  how  much  gelatin  it  may  con- 
tain, cannot  induce  any  growth  whatever  in  a  young  animal.  Lot 
652,  however,  grew  at  the  optimum  rate.  This  result  shows  that  the 
added  gelatin  made  good  a  limited  supply  of  certain  amino-acids  in 
the  wheat  proteins  of  the  diet.  This  formed  the  limiting  factor  in 
determining  the  slow  rate  of  growth  in  Lot  493.  Gelatin  is  shown  by 
this  experiment  to  supplement  well  the  proteins  of  the  wheat  kernel. 

Lots  756  and  785,  show  the  stunting  of  young  rats  fed  diets  which 
derived  their  protein  entirely  from  a  mixture  of  peas  and  gelatin, 
and  a  mixture  of  na\'y  beans  and  gelatin  respectively.  Both  diets 
contained  about  18  per  cent  of  protein.    When  of  good  quality  this 


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LEGENDS  TO  THE  CHARTS  173 

amount  suffices  for  the  support  of  normal  growth.  Combinations 
of  pea  proteins  with  gelatin,  and  of  bean  proteins  with  gelatin,  yield 
amino-acid  mixtures  which  are  deficient  in  some  way. 

In  Period  2  in  both  cases,  the  diets  differed  from  those  of  Period  1, 
only  in  that  the  gelatin  was  replaced  by  an  equal  amount  of  casein 
from  milk.  This  change  led  to  great  improvement  in  the  qualitj'-  of 
the  protein  in  the  diets,  and  growth  at  once  proceeded  at  a  good  rate. 
Gelatin  does  not  greatlj'  enhance  the  value  of  the  proteins  of  either 
the  pea  or  the  bean,  whereas  casein  does. 

Lots  646  and  647  show  the  effect  on  growth,  of  feeding  a  diet  con- 
taining but  9  per  cent  of  protein  derived  solely  from  rolled  oats 
(Lot  646),  and  the  same  diet  with  10  per  cent  of  carbohydrate  re- 
placed b}^  gelatin.  In  the  former  case,  growth  was  early  suspended, 
but  in  the  latter,  growth  proceeded  at  the  optimum  rate  to  full 
maturity.  This  result  shows  that  gelatin  supplements  the  proteins 
of  the  oat  kernel  in  a  very  satisfactory  manner.  (See  discussion 
under  Lots  493  and  652.) 

Lots  649  and  651,  show  the  growth  curves  of  rats  fed,  in  the  former 
case  a  diet  which  derived  its  protein  content  of  about  7  per  cent 
entirely  from  the  corn  kernel,  and  in  the  latter  case  the  same  diet 
^dth  10  per  cent  of  its  carbohydrate  replaced  by  gelatin.  In  marked 
contrast  to  the  effects  of  feeding  gelatin  together  with  wheat  or  oat 
proteins,  there  is  no  improvement  in  the  quality  of  corn  proteins 
through  combining  these  with  gelatin.  Gelatin  does  not  supplement 
the  peculiar  amino-acid  deficiencies  of  the  corn  kernel. 

Chart  9. — The  records  in  this  chart  give  an  idea  of  the  values  of 
the  proteins  derived  from  mixtures  of  two  seeds.  Each  of  the  diets 
described  contained  9  per  cent  of  protein.  It  has  been  estabhshed 
that  this  content  of  protein  in  a  ration,  when  it  is  derived  from  either 
the  wheat,  corn  or  rice  kernel  alone,  does  not  support  groA^-th  at  a 
rate  much  faster  than  half  the  normal  rate.  We,  therefore,  fed  a 
series  of  diets  in  which  the  protein  content  was  adjusted  at  this  level, 
and  derived  from  combinations  of  two  seeds,  in  order  to  find  the 
most  fortunate  combinations  of  seeds  as  sources  of  proteins  for 
gro^^'th.  Normal  growth  is  secured  on  diets  of  this  character,  only 
in  those  cases  where  the  proteins  of  one  seed  enhance  those  of  the 
other  seed  present  in  the  diet.  We  have  not  been  able  to  find  any 
two  seeds  whose  proteins,  when  fed  together  even  approximate  the 
value  of  the  proteins  of  milk. 


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LEGENDS  TO  THE  CHARTS  175 

Lot  1366,  derived  3  per  cent  of  protein  from  millet  seed  and  6  per 
cent  from  the  soy  bean.  The  deficiencies  of  the  diet,  aside  from  the 
character  of  the  proteins,  were  all  made  good  by  suitable  additions 
of  salts  and  butter  fat.  On  this  diet  the  growth  was  slow,  and  the 
animals  remained  undersized.  On  this  diet  three  females  have  pro- 
duced four  litters  (23)  young  of  which  but  three  individuals  were 
weaned,  the  others  being  allowed  to  die  in  infancy.  This  protein 
mixture  is  of  relatively  low  biological  value. 

Lot  1339  derived  6  per  cent  of  protein  from  rolled  oats  and  3  per 
cent  from  flaxseed  oil  meal.  Two  females  grew  up  on  this  diet. 
One  remained  sterile,  and  the  other  produced  but  one  litter  of 
young  (7).  These  were  finally  weaned  after  a  long  period  of  infancy 
in  which  their  growth  was  very  slow.  They  were  very  small  and 
runty  when  weaned.  A  protein  mixture  derived  from  these  two 
seeds  is  of  relatively  poor  quahty. 

Lot  1338  derived  6  per  cent  of  protein  from  the  wheat  kernel  and 
3  per  cent  from  flaxseed  oil  meal.  Growth  was  below  the  normal 
rate,  and  two  females  have  produced  but  three  litters  (18)  young. 
But  five  of  these  were  successfully  weaned.  Proteins  derived  from 
these  two  seeds  are  of  relatively  low  biological  value.  They  sufficed 
for  the  support  of  a  fair  rate  of  growth,  but  not  for  the  additional 
strain  of  reproduction.  This  mixture  must  have  both  protein  and 
fat-soluble  A  additions  in  order  to  produce  the  optimum  results  in 
nutrition. 

Chart  10. — Like  the  preceding  chart,  this  shows  the  relative 
biological  values  of  the  protein  mixtures  derived  from  mixtures  of 
two  seeds.  The  diet  was  made  adequate  in  every  respect,  except 
the  protein,  which  was  in  all  cases  adjusted  so  as  to  form  9  per  cent 
of  the  food  mixture.  The  reason  for  this  has  been  made  clear  in  the 
discussion  of  Chart  9. 

Lot  1350  derived  6  per  cent  of  protein  from  rye,  and  3  per  cent 
from  flaxseed  oil  meal.  Growth  fell  slightly  below  the  normal 
expectation.  One  female  and  her  daughter  have  produced  five  litters 
(30)  young,  of  which  but  five  individuals  have  been  reared.  This 
diet  is  not  quite  satisfactory  as  is  shown  by  the  reproduction  records, 
and  because  of  the  poor  quahty  of  its  proteins,  and  shortage  of  fat- 
soluble  A. 

Lot  1375  secured  6  per  cent  of  protein  from  rye  and  3  per  cent 
from  millet  seed.    One  female  which  grew  up  on  this  diet  has  had 


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S  W  V  U  9 


LEGENDS  TO  THE  CHARTS  177 

two  litters  of  young,  all  of  which  were  allowed  to  die  in  infancy. 
Another  female  remained  sterile.  It  is  e\'ident  that  this  combination 
of  proteins  does  not  form  a  fortunate  mixture. 

Lot  1378  derived  6  per  cent  of  protein  from  peas  and  3  per  cent 
from  millet  seed.  Growth  on  this  diet  was  slower  than  the  normal 
expectation,  and  reproduction  was  below  normal.  Two  females 
produced  four  litters  (17)  of  young,  of  which  but  nine  indi\'iduals 
were  finally  weaned  at  an  advanced  age.  These  were  very  small  for 
their  age.  Combinations  of  pea  and  millet  seed  proteins  do  not 
appear  to  have  a  very  high  biological  value. 

These  histories  selected  from  a  long  series  of  similar  experiments 
in  our  records  make  it  clear  that  it  is  not  easy  to  find  mixtures  of 
two  seeds  whose  proteins  are  of  such  a  character  as  to  supplement 
each  other's  deficiencies,  in  the  3'ields  of  certain  amino-acids,  and 
produce  mixtures  of  high  biological  value  for  growth  and  the  promo- 
tion of  physiological  well-being.  In  order  to  demonstrate  the  effects 
of  a  limited  protein  content,  or  of  proteins  of  poor  quality  in  the  diet, 
experiments  must  be  continued  over  a  relatively  long  period  of  time. 
Observations  of  man  or  animals  on  such  diets  may  lead  to  faulty 
deductions  when  the  experiments  are  of  short  duration. 

Chart  11. — This  chart  illustrates  in  a  general  way  the  content  of 
the  two  unidentified  dietary  essentials,  fat-soluble  A  and  water- 
soluble  B,  in  certain  natural  foods.  The  diet  in  aU  cases  consisted 
principally  of  purified  food  substances,  and  was  adequate  for  the 
support  of  growth,  except  that  its  content  of  fat-soluble  A  and 
water-soluble  B  was  derived  from  the  small  addition  of  natural  food. 
As  wiU  appear  from  the  records  in  Chart  12,  these  additions  of  natural 
food-stuffs,  probably  furnished  a  sufficient  amount  of  water-soluble 
B  to  support  normal  growth,  so  it  may  fairly  be  said  that  these 
records  afford  more  nearly  an  estimation  of  the  content  of  fat-soluble 
A  in  each  of  the  natural  foods  emploj^ed. 

Lot  723  shows  that  20  per  cent  of  flaxseed  does  not  supply  enough 
of  the  fat-soluble  A  to  support  normal  growth  in  a  young  rat. 

Lot  716,  shows  that  25  per  cent  of  millet  seed  supplied  enough  of 
both  the  unidentified  dietary  essentials  for  the  support  of  nearly 
normal  growth,  and  induced  sufficienth'  good  nutrition  to  make 
possible  the  production  of  nearly  the  normal  number  of  young. 
The  female  rat  usually  produces  five  litters  of  young  before  she 
reaches  the  age  of  fourteen  months,  which  age  marks  the  end  of  her 


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5  W  V  U  O 


LEGENDS  TO  THE  CHARTS  179 

period  of  fertility.  The  rat  whose  curve  is  shown,  had  four  Utters 
during  the  first  thirteen  months  of  her  hfe.  The  first  two  Utters  died 
early,  but  the  third  and  fourth,  which  were  born  after  butter  fat 
(more  fat-soluble  A)  was  added  to  the  mother's  diet,  were  success- 
fully brought  to  weaning  age. 

Lot  633,  whose  diet  derived  both  the  unidentified  dietarj^  essentials 
from  its  content  of  20  per  cent  of  alfalfa  leaf,  remained  distinctly 
undersized,  and  produced  but  two  Utters  of  young,  aU  of  which  died 
in  early  infancy. 

Lot  632,  which  received  but  10  per  cent  of  alfalfa  as  its  sole  source 
of  fat-soluble  A  and  water-soluble  B,  grew  slowly,  and  never  reached 
a  body  weight  greater  than  half  the  normal  adult  size,  and  produced 
no  young. 

Lot  631  was  unable  to  grow  at  all  when  restricted  to  5  per  cent 
of  aKalfa  leaf  as  its  sole  source  of  both  the  unidentified  dietary 
essentials,  but  responded  at  once  with  growth  when  the  content  of 
leaf  was  raised  to  30  per  cent. 

Lot  710  failed  to  grow  weU  when  restricted  to  a  diet  which  derived 
its  fat-soluble  A  and  water-soluble  B  from  15  per  cent  of  hemp  seed. 
The  oil  seeds,  judging  from  the  limited  data  available,  seem  to  con- 
tain more  of  the  fat-soluble  A  than  do  the  cereal  grains,  but  less  than 
millet  seed.  The  latter  is  richer  in  this  substance  than  any  other 
seed  yet  studied. 

Chart  12. — These  records  were  obtained  with  diets  which  derived 
their  content  of  water-soluble  B  entirely  from  the  amount  of  natural 
food-stuff  which  each  contained.  The  basal  diet  consisted  of  purified 
protein,  carboh^'drate,  a  suitable  mineral  salt  mixture,  and  butter 
fat  to  furnish  the  fat-soluble  A.  The  curves  give  an  approximate 
idea  of  the  minimum  amount  of  each  of  several  natural  food-stuffs 
which  are  necessary  to  furnish  sufficient  water-soluble  B  to  enable  a 
young  rat  to  grov.^  and  reproduce. 

Lots  645,  475  and  676  demonstrate  the  relative  richness  of  the 
wheat  kernel  in  water-soluble  B.  Even  15  per  cent  furnishes  enough 
to  enable  a  young  rat  to  grow  to  approximately  the  full  adult  size, 
and  to  produce  several  litters  of  young.  None  can  be  successfully 
weaned  on  this  diet.  Even  with  25  per  cent  of  wheat  in  the  diet, 
we  have  not  seen  a  litter  of  young  brought  to  the  weaning  age  when 
the  mother  was  restricted  to  this  type  of  diet.  When  the  wheat  is 
increased  to  35  per  cent  of  the  food  mixture  some  young  can  be 


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Ration: 
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Lot  1423 

Ration: 
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Potato 
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Casein 
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S  W  V  M  o 


LEGENDS  TO  THE  CHARTS  181 

reared,  but  the  mortality  is  still  very  high.  With  higher  levels  of 
wheat  substituted  for  carbohydrate  in  this  formula,  the  successful 
rearing  of  young  becomes  the  rule. 

Lot  695  shows  that  25  per  cent  of  cooked  peas  in  the  diet  as  the 
sole  source  of  water-soluble  B  furnishes  a  sufficient  amount  of  this 
substance  to  enable  young  rats  to  grow  well  and  produce  young. 
None  were  reared  by  any  of  the  female  rats  in  this  lot.  The  peas 
were  soaked  in  water  and  heated  for  an  hour  and  a  quarter  in  an 
autoclave  at  fifteen  pounds  pressure,  dried  and  ground.  This  treat- 
ment is  approximately  the  equivalent  of  the  heat  employed  in  the 
processing  of  canned  fruits  and  vegetables.  There  seems  to  be  little 
loss  of  water-soluble  B  as  the  result  of  such  heating. 

Lot  696  shows  that  25  per  cent  of  navj'  beans,  which  had  been 
soaked  and  heated  in  a  manner  similar  to  that  described  for  peas 
(Lot  695),  supplied  enough  of  water-soluble  B  to  enable  rats  to  grow 
to  full  adult  size  and  reproduce.  Eight  young  out  of  eighteen  young 
(2  litters)  were  reared  by  mothers  confined  to  this  diet. 

Chart  13. — It  has  been  pointed  out  (page  46)  that  the  tuber 
and  the  edible  root  are  both  storage  organs,  and,  therefore,  poor  in 
cellular  structures,  and  that  their  dietary  properties  are  very  closely 
similar  to  the  seeds.  The  records  of  young  rats  which  were  fed  mix- 
tures of  potato  and  peas,  supplemented  in  various  waj's  according 
to  the  biological  method  of  food  analysis,  demonstrates  the  truth 
of  this  assertion. 

Lot  1405  illustrates  the  slow  growth  and  early  death  of  a  rat  fed 
a  mixture  of  peas  and  potato,  supplemented  with  the  mineral  el- 
ements, calcium,  sodium  and  chlorine.  An  inspection  of  the  remain- 
ing curves  in  the  chart  reveals  the  fact  that  the  diet  is  still  deficient 
with  respect  to  fat-soluble  A,  and  in  no  other  respect. 

Lot  1450,  Period  1,  shows  the  failure  of  animals  to  grow  when  fed 
peas,  potato  and  fat-soluble  A.  When  in  Period  2,  pure  sodium 
chloride  (common  salt)  and  calcium  carbonate  (chalk)  were  added, 
growth  became  possible  at  the  normal  rate.  Two  Utters  of  young 
have  been  born  and  all  were  successfully  weaned.  This  result  in- 
dicates that  the  protein  content  derived  from  peas  and  potato  is 
of  satisfactory  character,  and  this  conclusion  is  supported  by  the 
records  of  Lot  1414,  which  has  been  successful  in  growth  and  repro- 
duction when  restricted  to  this  protein  mixture.  To  this  mixture  of 
peas  and  potato,  both  the  inorganic  content  and  the  content  of  fat- 


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6  N  V 


LEGENDS  TO  THE  CHARTS  183 

soluble  A  must  be  modified  by  suitable  additions  in  order  to  make  it 
dietetically  complete. 

Lot  1423,  Period  1,  shows  failure  of  animals  to  grow  on  a  diet  of 
peas  and  potato  supplemented  with  purified  protein.  In  Period  2, 
fat-soluble  A  was  added,  but  still  growth  could  not  take  place.  In 
Period  3,  the  addition  of  calcium,  sodium  and  chlorine,  rendered  the 
diet  complete.  Two  females  have  produced  three  litters  (24)  young, 
of  which  16  have  been  successfully  weaned,  and  the  remaining  ones 
are  apparently  normal,  but  under  weaning  age. 

Lot  1414  shows  that  good  growth  and  reproduction  are  possible 
on  a  diet  derived  from  peas  and  potato,  supplemented  wdth  the 
necessary  salts  and  fat-soluble  A,  and  gives  an  idea  of  the  quality  of 
the  protein  mixture  derived  from  these  sources.  It  is  of  interest  to 
note  that  the  proteins  of  the  pea  when  taken  in  the  amount  furnished 
by  this  diet  (about  18  per  cent)  and  forming  the  sole  proteins  of  the 
diet,  do  not  support  normal  growth  even  when  the  diet  is  made  com- 
plete with  respect  to  all  other  factors.  The  proteins  of  the  potato 
are  of  such  a  nature  as  to  enhance  the  value  of  the  proteins  of  the 
pea. 

In  preparing  these  food  materials  the  potatoes  were  steamed, 
skinned,  dried  and  ground.  The  peas  were  soaked,  heated  in  an 
autoclave  at  fifteen  pounds  pressure  for  an  hour  and  a  half,  dried 
and  ground.  The  ingredients  of  the  diet  were  ground  so  as  to  make 
it  impossible  for  the  rats  to  pick  out  and  eat  them  separately. 

Chart  14. — These  records  illustrate  the  dietary  properties  of  a 
mixture  of  the  corn  kernel  and  potato.  Like  the  preceding  chart 
they  show  that  this  mixture  closely  resembles  a  mixture  of  two  seeds, 
and  supports  the  view  that  the  storage  tissues  of  plants  all  resemble 
each  other  in  their  dietary  properties. 

Lot  1397  shows  the  failure  of  the  animals  to  grow  when  fed  a 
mixture  of  corn  and  potato  supplemented  with  the  only  inorganic 
salts  necessary  to  complete  its  mineral  content.  That  no  other 
elements  are  necessary  is  made  clear  by  the  records  of  the  other 
animals  in  this  chart. 

Lot  1442,  Period  1,  shows  that  the  addition  of  fat-soluble  A,  with- 
out salts,  does  not  make  gro'wi'h  possible  on  a  mixture  of  potato  and 
corn  kernel.  In  Period  2,  growth  took  place  at  once  on  the  addition 
of  sodium  chloride  and  calcium  carbonate. 

Lot  1415,  Periods  1  and  2,  illustrate  the  fact  that  the  addition  of 


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s  w  V  a  o 


LEGENDS  TO  THE  CHARTS  185 

protein  (casein)  alone,  or  of  protein,  and  fat-soluble  A,  respectively, 
does  not  make  the  mixture  of  potato  and  corn  kernel  dietetically 
complete.  In  Period  3,  when  the  necessary  salts  were  added,  growth 
took  place  at  once.  The  rat  whose  curve  is  shown  has  successfully 
reared  two  litters  of  young  (14)  and  her  daughter,  from  the  first 
litter,  has  weaned  a  htter  of  seven  young.  The  daughter  has  been  fed 
exclusively  upon  the  diet  of  Period  3,  since  she  was  weaned.  These 
results  make  it  clear  that  this  mixture  of  corn,  casein,  potato,  butter 
fat  and  the  two  salts,  forms  a  very  satisfactory  diet. 

Lot  1408  shows  the  abihty  of  young  rats  to  grow  and  reproduce  at 
the  normal  rate  and  rear  part  of  their  young  when  confined  to  a  diet 
of  corn  and  potato  supplemented  with  fat-soluble  A  and  two  salts, 
calcium  carbonate  and  sodium  chloride.  This  record  indicates  that 
the  proteins  derived  from  these  two  sources  are  of  fairly  good  biolog- 
ical value.  The  diet  contains  but  9  per  cent  of  total  crude  protein 
(N  X  6.25).  If  the  protein  were  all  derived  from  the  corn  kernel,  this 
amount  would  not  support  such  a  good  rate  of  growth,  and  no  rearing 
of  young. 

From  the  data  available  in  our  records,  it  is  apparent  that  the 
potato  is  a  very  valuable  food,  a  conclusion  which  is  in  harmony 
with  the  favor  in  which  it  has  come  to  be  regarded  as  an  article  of 
diet  for  man. 

Chart  15. — This  and  the  following  chart  describe  the  relation  of 
the  mother  as  a  factor  of  safety  in  the  nutrition  of  her  young.  In 
nearly  all  of  these  records  the  mother  was  fed  during  lactation,  a  diet 
which  was  faulty  in  some  respect,  and  on  wliich  the  young,  after 
the  weaning  age,  could  not  grow  at  all.  The  problem  was  to  find 
to  what  extent  the  mother  is  able  to  take  such  faulty  diets,  and  pro- 
duce milk  of  a  character  wliich  will  support  growth  in  her  young. 
The  results  show  that  the  mother  is  capable  under  such  dietary 
limitations  of  providing  for  her  offspring  a  better  diet  for  growth 
than  she  herself  receives. 

The  mothers  were  fed  an  excellent  diet  until  they  delivered  their 
young.  The  htter  was  in  all  cases  reduced  to  four,  in  order  to  make 
the  results  comparable,  and  in  order  not  to  place  an  excessive  burden 
upon  the  mother.  From  the  day  the  young  were  born  the  mother 
received  the  faulty  experimental  diet. 

Rat  211  illustrates  the  rate  of  growi:h  of  a  Utter  of  four  young 
when  the  diet  of  the  mother  is  highly  satisfactory.    This  diet  con- 


186    THE  NEWER  KNOWLEDGE  OF  NUTRITION 

tained  a  liberal  amount  of  milk  and  of  wheat,  together  with  a  salt 
mixture  and  butter  fat. 

Rat  738  was  fed  nothing  but  rolled  oats.  Young  after  being 
weaned  cannot  grow  at  all  on  this  diet.  During  the  first  20  days  the 
young  grew  slowly,  then  became  stunted,  and  died  between  the  40th 
and  50th  daj'^s.  There  are  three  types  of  deficiency  in  rolled  oats: 
the  inorganic  content  is  unsatisfactory,  the  content  of  fat-soluble  A 
is  very  low,  and  the  proteins  are  not  of  very  high  value  for  growth. 
Notwithstanding  these  deficiencies,  the  lactating  mother  was  able 
to  produce  milk  having  considerable  growth-promoting  properties. 

Rat  843  was  fed  rolled  oats  with  one  of  its  deficiencies  corrected, 
viz :  by  the  addition  of  fat-soluble  A.  The  growth  curve  of  her  young 
shows  that  her  milk  was  of  distinctly  better  quahty  than  that  which 
she  could  have  produced  from  oats  alone.  The  young  grew  faster 
and  growth  continued  over  a  longer  interval.  Since  the  young  con- 
tinued to  grow  to  the  50  th  day,  it  is  evident  that  the  mother  was  still 
supplementing  the  diet  of  oats  and  butter  fat,  which  they  began  to 
eat  at  about  the  20th  day  of  age,  with  a  considerable  amount  of 
milk  which  corrected  the  inorganic  content  of  the  oat  kernel,  for 
without  the  addition  of  calcium,  sodium  and  cholrine,  rolled  oats 
cannot  support  growth,  even  when  its  other  deficiencies  are  corrected. 

Rat  983  did  no  better  with  her  young  on  a  diet  of  oats  to  which 
both  protein  and  fat-soluble  A  were  added,  than  did  rat  843,  with- 
out the  protein  addition.  The  first  limiting  factor  for  the  mother 
in  milk  production  is  the  inorganic  content,  just  as  it  is  for  growth 
in  the  young. 

Rat  899  did  remarkably  well  in  inducing  growth  in  her  young 
when  her  diet  consisted  of  rolled  oats  and  a  suitable  addition  of  salts 
for  the  correction  of  the  inorganic  deficiencies  of  the  oat  kernel. 
The  seed  is  not  entirely  free  from  fat-soluble  A,  and  the  mother  seems 
to  have  a  reserve  supply  of  this  substance  in  her  tissues  which  she 
can,  for  a  time,  contribute  to  her  milk. 

Rat  1978,  which  was  fed  oats  supplemented  with  salts  and  fat- 
soluble  A,  induced  growth  at  a  fairly  good  rate  in  her  young.  The 
60  per  cent  of  oats  in  her  diet  furnished  but  9  per  cent  of  protein, 
and  this  did  not  suffice,  because  of  its  relatively  low  value,  for  the 
production  of  a  normal  milk  supply.  The  growth  of  these  young 
after  the  time  they  became  able  to  eat  of  the  mother's  food  supply, 
was  much  more  rapid  than  it  would  have  been  had  they  not  been 


LEGENDS  TO  THE  CHARTS       187 

getting  a  supplementary  milk  supply  from  the  mother  during  the 
period  covered  by  the  growth  curve. 

Chart  16  contains  further  records  of  the  growth  of  young  which 
were  suckling  mothers  on  diets  derived  from  rolled  oats,  supple- 
mented in  various  ways. 

Chart  16. — Continuing  the  records  described  in  Chart  15. 

Rat  948  shows  the  failure  of  the  young  to  develop  beyond  a  lim- 
ited degree  on  a  diet  of  rolled  oats  supplemented  with  protein  only. 
The  behavior  of  these  3'oung  is  comparable  to  that  of  Lot  738, 
Chart  16.  The  two  most  serious  deficiencies  of  the  oat  kernel  for 
milk  production  as  for  growth  in  the  young,  are  the  inorganic  factor 
and  the  shortage  of  fat-soluble  A. 

It  was  shown  in  Chart  8  that  oat  proteins  combined  with  gelatin, 
form  a  highly  satisfactory  protein  mixture.  This  is  confirmed  by 
the  growth  at  half  normal  rate  of  the  young  of  rat  949,  whose  diet 
consisted  of  rolled  oats  and  gelatin.  Young  rats  cannot  grow  at 
all  on  this  mixture.  The  mother  is  able  to  take  such  a  faulty  diet, 
and  furnish  milk  of  such  a  character  as  will  safeguard  her  young  in 
a  most  remarkable  degree.  Her  limitations  are,  however,  easily 
apparent. 

Rat  984  did  slightly  better  in  extending  the  lives  of  her  young 
when  she  was  fed  rolled  oats  plus  gelatin  plus  butter  fat  (fat-soluble 
A),  than  did  rat  949,  on  the  same  food,  minus  the  butter  fat.  It 
should  be  remembered  that  young  rats  cannot  grow  at  all,  if  when, 
after  being  weaned,  they  are  confined  to  this  diet.  The  role  of  the 
mother  as  a  factor  of  safety  in  the  nutrition  of  her  young  is  easily 
seen. 

Rat  1020,  which  was  fed  oats,  gelatin  and  salts,  was  limited  only 
with  respect  to  the  relative  shortage  of  fat-soluble  A  in  her  diet. 
Nevertheless,  she  was  able  to  produce  milk  which  could  induce 
growth  at  a  fairly  good  rate  in  her  young. 

Rat  1019,  was  fed  a  diet  which  differed  from  that  of  1020  only  in 
containing  casein.  This  appears  to  have  had  a  slightly  beneficial 
effect. 

Rat  980  was  fed  rolled  oats  plus  20  per  cent  of  skim  milk  powder. 
This  amount  was  not  sufficient  to  correct  the  inorganic  deficiencies 
of  the  diet,  and  failed  to  supply  enough  fat-soluble  A  to  render  the 
diet  satisfactory  for  milk  production.  It  seems  probable  that  the 
sodium  chloride  content  and  fat-soluble  A  in  the  skim  milk  powder 


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LEGENDS  TO   THE  CHARTS  189 

were  the  limiting  factors  in  preventing  the  production  of  normal  milk 
in  this  case. 

In  answer  to  the  question  as  to  whether  the  failure  of  the  young 
to  grow  on  the  milk  they  received  in  these  experiments,  was  not  the 
result  of  insufficiency  in  quantity  rather  than  quaUty  of  milk,  we 
have  the  observations  on  cows,  which  were  fed  insufficient  food 
during  lactation,  and  in  other  experiments,  in  which  cows  were 
starved  for  common  salt  for  periods  of  eight  to  fifteen  months,  and 
actually  died  or  came  near  death  from  salt  starvation.  Under  such 
conditions  the  milk  flow  was  kept  up  over  a  long  period  in  a  most 
surprising  manner. 

We  have  further  evidence  that  the  young  rats  in  the  experiments 
described,  continued  in  some  instances  to  grow  long  after  they  be- 
came able  to  eat  of  their  m.other's  food,  when  the  latter  was  of  such 
a  character  as  to  permit  of  no  growth  whatever,  had  it  not  been 
supplemented  with  a  considerable  amount  of  milk  from  the  mother. 
When  it  is  considered  that  in  some  of  these  cases  the  young  weighed 
more  than  half  as  much  as  the  mother,  it  must  be  admitted  that  the 
milk  production,  even  in  these  greatly  prolonged  periods  of  lactation, 
while  the  mothers  were  taking  faulty  diets,  must  have  been  very 
considerable. 

The  relation  between  the  character  of  the  diet  of  the  nursing 
mother  and  the  character  of  the  milk  she  produces  has  been  dis- 
cussed in  Chapter  6. 


BIBLIOGRAPHY 
Chapter  I 

1.  Fischer:  Chemistry  of  the  Proteins,  Mann. 

2.  Osbome,  T.  B.:  The  Vegetable  Proteins,     Monographs  on 

Biochemistry,  Longmans,  Green  and  Company. 

3.  Atwater,  W.  A.:  Bulletin  28,  United  States  Department 

of  Agricultm-e. 

4.  Eijkman,  C:  Arch.  f.  Hyg.,  1906,  hdii,  150. 

Arch.  path.  Anat.,  1897,  cxlviii,  523. 

5.  Henriques  and  Hansen:  Zeitschr.  fiir  physiol.  chem.,  1905, 

xliii,  417. 

6.  WiUcock,  E.G.,  and  Hopkins,  F.  G.:  Jour.  Physiol.,  1906, 

XXXV,  88. 

7.  Wise.  Agric.  Expt.  Sta.,  Research  Bull.,  No.  17  (1911). 

8.  McCoUum,  E.  V.,  and  Davis,  M.:  Jour.  Biol.  Chem.,  1913, 

XV,  167. 

9.  Stepp,  W.:  Biochem.  Ztschr.,  1909,  xxii,  452;  Ztschr.  f. 

Biol.,  1912,  Ivii,  135;  Ibid,  1912-1913,  lix,  366. 

10.  Hopkins,  F.  G.:  Jour.  Physiol.,  1912,  xliv,  425. 

11.  Funk,  C:  Lancet,  London,  1911,  ii,  1266. 

12.  Eraser,  H.,  and  Stanton,  A.  T.:  Lancet,  London,  March  12, 

1910,  733;  The  Etiology  of  Beri-Beri,  Study  12,  from 
the  Institute  for  Medical  Research,  Federated  Malay 
States,  1911. 

13.  McCollum  and  Davis:  Jour.  Biol.  Chem.,  1915,  xxiii,  247; 
McCollum,  E.  v.,  Simmonds,  N.,  and  Pitz,  W.:  Ibid,  1916, 

xx^/,  105. 

14.  Funk  and  Macallum:  Jour.  Biol.  Chem.,  1915,  xxiii,  419. 

15.  Henry,  W.  A.:  Wisconsin  Agric.  Expt.  Sta.,  Annual  Re- 

port, 1889,  15. 

191 


192  BIBLIOGRAPHY 

16.  Funk,  C:  J.  State  Med.,  1912,  xx,  341;  Biochem.  Bull., 

1915,  iv,  304. 

17.  McCollum  and  Davis:  Jour.  Biol.  Chem.,  1915,  xxiii,  181. 

18.  McCollum  and  Davis:  Jour.  Biol.  Chem.,  1915,  xxiii,  231. 

19.  McCollum,  E.  V.,  and  Kennedy,  C:  Jour.  Biol.  Chem., 

1916,  xxiv,  491. 

20.  Osborne,  T.  B.,  and  Mendel,  L.  B.:  Jour.  Biol.  Chem., 

1913,  xvi,  431. 

Chapter  II 

1.  McCollum,  Simmonds  and  Pitz:  Jour.  Biol.  Chem.,  1917, 

xxix,  341. 

2.  Smith,  Theobold:  Bureau  of  Animal  Industry,  Bacilli  in 

Smne  Disease,  1895-1896,  172. 

3.  Hoist,  A.,  and  Frohch,  T.:  Z.  Hyg.  u.  Infektionskrankh, 

1913,  Ixxv,  334. 

4.  McCoUum  and  Pitz:  Jour.  Biol.  Chem.,  1917,  xxxi,  229. 

5.  McCollum  and  Simmonds:  Jour.  Biol.  Chem.,  1917,  xxxii, 

181. 

6.  McCollum   and   Simmonds:   Jour.    Biol.    Chem.,    1918, 

xxxiii,  55. 

7.  Hart,  E.  B.,  McCollum,  E.  V.,  Steenbock,  H.,  and  Hum- 

phery,  G.  C:  Wise.  Agric.  Expt.  Sta.  Research  Bull., 

17,  1911. 
Hart  and  McCollum:  Jour.  Biol.  Chem.,  1914,  xix,  373. 
McCollum  and  Davis:  Jour.  Biol.  Chem.,  1915,  xxi,  615. 
McCollum,  Simmonds  and  Pitz:  Ibid,  1916-1917,  xxviii, 

211. 

8.  Hart  and  McCollum:  Jour.  Biol.  Chem.,  1914,  xix,  373. 
McCollum,  Simmonds  and  Pitz:  Ibid,  1916,  xxviii,  153. 

9.  McCollum,  E.  V.,  Simmonds,  N.,  and  Parsons,  H.  T.: 

Unpublished  data. 
10.  McCollum,  E.  V. :  Jour.  Am.  Med.  Assn.,  1917,  kviii,  1379. 
Harvey  Lecture  Series  1916-1917 — also — Unpubhshed 
data. 


BIBLIOGRAPHY  193 

U.  iMcCoUum,  Simmonds  and  Pitz:  Jour.  Biol.  Chem.,  1917, 

Xxix,  521.  -r^.    ,     /-,!  ini7 

12.  McCoUum,  Simmonds  and  Pitz:  Jour.  Biol.  Chem.,  1917, 
XXX,  13. 

Chapter  III 

1.  Slonaker,  J.  R.:  Leland  Stanford  Junior  University,  Pub. 

rniv.  Series,  1912.  ^.  ,   r^^  ini7 

2.  McColliun,  Simmonds  and  Pitz:  Jour.  Biol.  Chem.,  1917, 

XXX,   io.  .  1  ni « 

3.  TylcCollum,  Simmonds  and  Pitz:  Am.  Jour.  Physiol.,  191b, 

xliv,  333.  .. 

4   E^^'ard  J.  M.:  Proc.  Iowa  Acad.  Sci.,  191o,   xxu,  cJ/o. 
5'.  Loeb,  J.:  The  DjTiamics  of  Living  Matter,  New  York, 

6.  Howell,  W.  H.:  Am.  Jour.  Physiol.,  1899,  ii,  47;  1902,  vi, 
181. 

Chapter  IV 

1.  McCollum,  E.  v.:  Jour.  Biol.  Chem.,  1914,  xix,  323. 

2.  jNIcCoUum  and  Simmonds:  Jour.  Biol.  Chem.,  1917,  xxxii, 

347.  „ 

3    McCollum  and  Davis:  Jour.  Biol.  Chem.,  191o,  xx,  4io. 
4.  McCoUum,  Simmonds  and  Parsons:  Unpublished  data. 

Chapter  V 

1.  McCollum  and  Kennedy:  Jour.  Biol.  Chem.,  1916,  xxiv, 

491. 

2.  Osborne  and  Mendel:  Jour.  Biol.  Chem.,  1913,  x^i,  431._ 

3.  McCollum  and  Simmonds:  Jour.  Biol.  Chem.,  1917,  xxxu, 

347. 

4.  ISIcCollum,  Simmonds  and  Parsons:  Unpublished  data. 

5.  Herdhka,  A.:  Bulletin  34,  Bureau  of  American  Etlmology. 


194  BIBLIOGRAPHY 

6.  Mori,  M.:  Jahrb.  Kinderheilk,  1904,  lix,  175. 

7.  Bloch,  C.  E.:  Ugeskruft  fiir  Laeger,  1917,  Ixxix,  349,  cited 

from  Jour.  Am.  Med.  Assn.,  1917,  lx\iii,  1516. 

8.  Czerny,  A.  and  Keller,  A.:  Des  Kindes,  Leipsic,  1906,  pt. 

2,67. 

9.  Little,  A.  D.:  Jour.  Am.  Med.  Assn.,  1912,  Iviii,  2029. 

10.  Walcott,  A.  M.:  Jour.  Am.  Med.  Assn.,  1915,  Ixv,  2145. 

11.  Eijkman,  C:  Arch.  f.  Hyg.,  1906,  Iviii,  150. 

Arch.  Path.  Anat.,  1897,  cxlviii,  523. 

12.  Funk,  C:  Lancet,  London,  1911,  ii,  1266. 

13.  Funk  and  Macallum:  Jour.  Biol.  Chem.,  1915,  xxiii,  419. 

14.  Williams,  R.  R.:  Jour.  Biol.  Chem.,  1916,  xxv,  437;  1916, 

xxvi,  431;  1917,  xxix,  495. 

15.  Jackson,  L.,  and  Moore,  J.  J.:  Jour.  Infect.  Dis.,  1916,  xix, 

478. 

16.  McCollum  and  Pitz:  Jour.  Biol.  Chem.,  1917,  xxxi,  229. 

17.  Hess,  A.  F.:  Am.  Jour.  Dis.  of  Children,  1917,  xiv,  337. 

18.  Goldberger,  Joseph:  Jour.  Am.  Med.  Assn.,  1916,  Ixvi,  471. 

19.  Jobling,  J.  W.,  and  Peterson,  W.:  Jour.  Infect.  Dis.,  1916, 

xviii,  501. 

20.  Thompson-MacFadden  Commission,   Siler,   J.  F.,  Garri- 

son, P.  E.,and  McNeal,  W.  J.:  Archiv.  Int.  Med.  Oct. 

1914,  p.  453;  Journ.  Amer.  Med.  Assn.  Sept.  26,  1914, 
p.  1090. 

21.  Goldberger,  Joseph:  Public  Health  Reports,  November  17, 

1916,  pp.  3159-3173. 

22.  Goldberger,   Joseph:   Public  Health  Reports,  Nov.    12, 

1915,  p.  3. 

23.  Chittenden,  R.  H., and  Underbill,  F.  P. :  Am.  Jour.  Physiol., 

1917,  xliv,  13. 

24.  McCollum,  Simmonds  and  Parsons:  Jour.  Biol.  Chem., 

1918,  xxxiii,  411. 

25.  McCollmn    and    Simmonds:   Jour.    Biol.    Chem.,    1917, 

xxxii,  29. 

26.  Hess,  A.  F. :  Jour.  Am.  Med.  Assn.,  1918,  kx,  900. 


BIBLIOGRAPHY  195 

Chapter  VI 

1.  McCollum  and  Simmonds:  Am.  Jour.  Phys.,  1918,  xlvi, 

275. 
McColluni,  Simmonds  and  Pitz:  Joiir.  Biol.  Chem.,  1916, 
xx\ii,  33. 

2.  Osborne  and  Mendel:  Jour.  Biol.  Chem.,  1915,  xx,  379. 

3.  Andrews,  V.  L.:  Philippine  Jom*.  Science,  Series  B,  1912, 

vii,  67. 

4.  Babcock,  S.  M.:  Twenty-Second  Annual  Report  of  Wis- 

consin Experiment  Station,  1905,  129. 

5.  Eckles,  C.  H.,and  Palmer,  L.  S.:  Missouri  Agric.  Expt. 

Station  Research  Bull.,  25,  1916. 

6.  Ducaisne,  E.:  Gaz.  Med.,  Paris,  1871,  317. 

Chapter  VII 

1.  Osborne  and  Mendel:  Jour.  Biol.  Chem.,  1915,  xx,  381. 

2.  McCollum  and  Da^^s:  Jour.  Biol.  Chem.,  1915,  xxiii,  247. 

3.  McCollum,  Simmonds  and  Pitz:  Jour.  Biol.  Chem.,  1917, 

xxix,  521. 

4.  Sullivan,  M.  X.,  and  Voegtlin,  C. :  Jour.  Biol.  Chem.,  1916, 

xxiv,  xvi. 

5.  Simpson  and  Edie:  1911-12,  Ann.  Trop.  Med.  and  Parasit., 

V,  321. 
Ohler:  Jour.  IVIed.  Research,  1914,  xxxi,  239. 

6.  Withers  and  Carruth :  Jour.  Agric.  Research,  1915,  v,  261. 

Jour.  Biol.  Chem.,  1917,  xxxii,  245. 

7.  McCollum  and  Da\as:  Jour.  Biol.  Chem.,  1915,  xxiii,  231. 

8.  McCollum  and  Simmonds:  1917,  xxxii,  181. 


INDEX 


Alfalfa  flour,  41,  167,  169,  179 
Alkaloids,  4 
Amino-acids,  5,  74,  75 
Appetite,  importance  of  in  the 
selection  of  food,  64 

Barley,  38 
Bean,  navy,  38,  181 
Bean,  soy,  38,  175 
Beri-beri,  7,  20,  28,  83,  90 
Biological  method  for  the  anal- 
ysis of  food-stuffs,  20,  21,  56, 
113,  161 
Butter  fat,  16,  89 

Carnivora,  dietary  habits  of,  78 
Cereal  grains,  157,  161 
Chittenden  and  Underhill,  stud- 
ies of  pellagra,  107 
Corn,  10,  173 
Cotton  seed  flour,  142,  143 

Deficiency  diseases,   83-87,   91 
95,  114 

Diet  and  disease,  6,  7 

Diet,  essential  factors  in,  31 

Diet  of  nursing  mother  in  rela- 
tion to  the  quality  of  her 
milk,  116-129,  185-189 

Diet,  planning  of  adequate,  130 

Diet,  monotonous,  7 

Dietary  essentials,  nomencla- 
ture of  unidentified,    32 


Dietary    essentials,     chemically 

unidentified,  23,  34,  47 
Dietary  habits,  139 
Diets  from  single  plant  sources, 

10 
Diets,  simplified,  9,  14,  15,   16, 

19,  155 
Disease  and  diet,  6,  30,  36,  87, 

95,  103,  139 
Diseases,  deficiency,  83-87,  91, 

95,  114 

Eggs,  80 

Eijkman,  7 

Eward,  studies  on  appetite,  64 

Fats,  2,  3,  4 

Fats,  butter,  16 

Fats,  egg  yolk,  16 

Fats,  lard,  16 

Fats,  vegetable,  16 

Fat-soluble  A,   23,   34,   47,   89, 

145,  155 
Flax  seed,  38 
Food  analysis,  5 
Foods,     effect    of    cooking    on, 

135-138 
Foods,    physical    properties   of, 

15 
Foods,  protective,  82,  141,  147, 

149 
Foods-stuffs,  biological  analysis 

of,  20,  21,  56 


197 


198 


INDEX 


Food-stiifTs,    supplementary   re- 
lationships among,  61,  71,  81 
Fraser  and  Stanton,  19 
Fruits,  7,  142 
Funk,  19 

Gelatin,  171 

Glandular  organs,  79 

Gliadin,  8 

Goldberger,  studies  of  pellagra, 

105-107 
Growth,  impetus  to,  72 

Henriques    and    Hansen,    stud- 
ies of  simplified  diets,  8 
Hess,  studies  of  scurvy,  100 
Hoist,  studies  of  scurvy,  34 
Hopkins,    studies   of   simplified 

diets,  18 
Hormones,  85 

Inorganic  salts,  importance  of, 

4,22 
Iron,  69 

Jobling    and    Peterson,    studies 
of  pellagra,  105-106 

Kafir  corn,  38 

Leaf,  dietary  properties  of,  the, 

41,  44,  53,  77 
Leaf  and  seed  mixtures,  dietary 

properties  of,  61,  167 
Lipoids,  3,  17 

Meats,  6,  8,  76 
Milk,  6,  8,  76 

Milk,  place  of  in  the  diet,  150- 
153 


Milk,  production,  12 

Milk,  quality  of,  as  influenced 

by  diet,  116-129,  185-189 
Millet  seed,  38,  175,  177 
Muscle  tissue,  6,  8,  76 
Nomenclature  of  the  chemically 

unidentified  dietary  essentials, 

84 

Osborne  and  Mendel,  87 

Pasteurization  of  milk,  100-103 
Peanut,  142 
Peas,  38,  177,  181 
Pellagra,  7,  30,  103 
Pellagra-producing  diets,  108 
Polyneuritis,  19,  20,  28 
Potato,  proteins  of,  135,  181 
Proteins,  2,  3,  4,  5 
Proteins,    biological    values    of, 

5,  24,  74,  75 
Proteins,  quality  not  shown  by 

chemical  analysis,  113 

Rat,  domestic,  14 

Rat,  domestic,  growth  of,  14 

Rat,  reproduction  in,  14 

Rice,  dietary  properties  of,  27, 

38,  159,  161 
Rickets,  111 
Roots,  edible,  47 
Rye,  dietary  properties  of,  38, 

175 

Salts,  4 

Scurvy,  7,  30,  34,  36,  37,  95-103 
Seed,  biological  properties  of,  53 
Seed,  and  leaf  mixtures,  dietary 
properties  of,  61 


INDEX  199 

Seeds,  dietary  properties  of,  6,  Variety  not  a  safeguard  in  nutri- 

165  tion,  66 

Slonaker,  studies  of  vegetarian  Vegetable  oils,  16 

diet,  57  Vegetables,  6,  7 

Smith,  Theobald,  scurvy  in  the  Vegetarian  diet,  50,  53 

guinea  pig,  34 

Sodium,   lack   of    sufficient,    in  Water,  4 

seeds,  23,  49  Water-soluble    B,    29,    34,    47, 

Starch,  2,  3,  4  155 

Stepp,  studies  of  dietary  prop-  Wheat  and  other  cereals  com- 

erties  of  lipoids,  17  pared,  139 

Wheat,    dietary    properties    of, 

Thompson-McFadden  CommJs-  10,  20,  21,  38,  157,  159,  171, 

sion,  studies  of  pellagra,   106  175,  179 

Tubers,    dietary   properties   of.  Wheat  flour,  bolted,  140 

6,  45  Wheat  flour,  whole,  140 

Unidentified  factors  in  the  diet,  Xerophthalmia  of  dietary  origin, 

17,  18  87,  139 


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HE   following   pages    contain    advertisements    of 
books  by  the  same  author  or  on  kindred  subjects 


Organic  Chemistry  for  Medical 
Students 


By   ELMER   V.    McCOLLUM,    Ph.D. 

Professor  of  Bio-Chemistry,  Johns  Hopkins  Medical  School 


Illustrated.     Cloth  ^  i2mo.     %2.2£ 

The  author  has  based  this  work  on  the  new  bio- 
logical methods  of  teaching  chemistry  to  medical 
students.  The  work  is  developed  from  Dr.  InIcCoI- 
lum's  unusual  researches  and  experiments  and  the 
subject  matter  is  presented  with  great  clearness  and 
attention  to  teaching  principles.  It  is  unique  in 
scope  and  methods  and  is  designed  for  the  use  of 
both  medical  and  pre-medical  students. 


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Chemistry  of  Food  and  Nutrition 

New  and  Revised  Edition 

By  henry  C.  SHERMAN 

Professor  of  Food  Chemistry  in  Columbia 
University 

$2.00 

This  new  edition,  entirely  rewritten  and  en- 
larged to  nearly  twice  the  original  size,  incor- 
porates the  recent  advances  in  all  of  the  topics 
considered  in  the  previous  edition  as  well  as 
some  new  topics  which  have  lately  become  im- 
portant to  the  student  of  food  and  nutrition. 

The  review  of  the  chemistry  of  the  organic 
foodstuffs  considered  in  the  first  edition  in  one 
chapter  is  now  treated  in  three  chapters  and 
contains  considerable  matter  of  distinctly  nu- 
tritional import.  The  chapters  on  digestion, 
metabolism,  food  requirements,  dietary  stand- 
ards and  economic  use  of  food  have  all  been  re- 
written and  expanded  to  embrace  recent  ad- 
vances. New  chapters  on  the  specific  relations 
of  food  to  growth  and  on  the  so-called  deficiency 
diseases  and  vitamine  theories  have  been  added. 


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Some  Aspects  of  Food  Economy 

By  MARY  S.  ROSE 

Everyday  Foods  in  War  Time  ^-^^ 

This  little  book  was  written  in  response  to  a  re- 
quest for  "a  war  message  about  food."  It  gives  a 
simple  explanation  of  the  part  which  some  of  our 
common  foods  play  in  our  diet,  and  points  out  how 
the  necessary-^  saving  of  fat,  fuel,  sugar,  and  meat  can 
be  made  without  a  loss  of  health  or  strength. 

There  are  chapters  on  the  Milk  Pitcher  in  the 
Home;  Cereals  We  Ought  to  Eat;  Meats  We  Ought 
to  Save;  The  Potato  and  Its  Substitutes;  Are  Fruits 
and  Vegetables  Luxuries?  Sugar  and  Spice  and 
Everything  Nice;  On  Being  Economical  and  Pa- 
triotic at  the  Same  Time. 

Feeding  the  Family  ^^^^ 

This  is  a  clear  concise  account  in  simple  everyday 
terms  of  the  ways  in  which  modern  knowledge  of  the 
science  of  nutrition  may  be  applied  in  ordinary  life. 
The  food  needs  of  the  members  of  the  typical  family 
group — ^men,  women,  infants,  children  of  various 
ages — are  discussed  in  separate  chapters,  and  many 
illustrations  in  the  form  of  food  plans  and  dietaries 
are  included.  The  problems  of  the  housewife  in 
tr>dng  to  reconcile  the  needs  of  different  ages  and 
tastes  at  the  same  table  are  also  taken  up,  as  are  the 
cost  of  food  and  the  construction  of  menus.  A  final 
chapter  deals  with  feeding  the  sick. 


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War  Bread 


By  ALONZO  E.  TAYLOR 
Professor  of  Physiological  Chemistry,  University  of  Penn- 
sylvania; member  of  the  United  States  Food  Admin- 
istration ^  ^^ 

S.60 

Dr.  Taylor  states  that  it  is  his  purpose  to  make  clear 
just  what  must  be  accomplished  in  order  that  we  may 
give  to  every  member  of  the  allied  people  his  full  share 
in  our  pooled  food  stuff  at  the  lowest  comparable  cost 
and  with  the  least  labor.  With  this  in  view,  he  takes  up 
the  following  topics: 

What  the  Allies  Need;  What  We  Possess;  Why  We  are 
Limited  in  Wheat;  Food  Value  of  the  Different  Grains; 
Ways  of  Stretching  Wheat;  and  Waste  of  Wheat. 


The  Food  Problem 


By  VERNON  KELLOGG  and  ALONZO  E.  TAYLOR 
With  an  Introduction  by  Herbert  Hoover 

SI. 25 
*'Food,"  says  JNIr.  Hoover  in  his  introduction,  ''is 
always  a  problem  in  every  phase  of  its  production,  han- 
dling, and  consumption.  It  is  a  problem  with  every 
farmer,  every  transporter  and  seller,  every  state  and 
nation.  And  now  very  conspicuously  it  is  a  problem  with 
three  great  groups;  namely,  the  Allies,  the  Central  Em- 
pires, and  the  Neutrals;  in  a  word,  it  is  a  great  inter- 
national problem." 

Some  of  the  questions  which  the  book  considers  in 
detail  are:  What  is  the  problem  in  detail?  What  are  the 
general  conditions  of  its  solution?  W^hat  are  the  imme- 
diate problems  and  particulars  which  concern  us?  and 
finally,  What  are  we  actually  doing  to  meet  the  problem? 


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